And that concludes our live coverage of Sunday's march in Paris in support of unity and the victims of last week's attacks, in which 17 people were killed. The French interior ministry has said it was the biggest demonstration in French history.
President Francois Hollande was joined by 40 world leaders who linked arms at the start of the marches. He said Paris was the capital of the world for the day.
There were also rallies in other French cities, across Europe, and around the world, from Beirut to Montreal.
You can follow further updates, as well as background material on the story, on the BBC News website.
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"The (French) Jewish community is in need of reassurance... Each new tragedy has the Jewish community more and more worried," Jack-Ivey Bohbot told BFMTV.
Imelda Flattery, BBC News
@ImeldaFlattery
BBCCopyright: BBC
tweets: London's Tower Bridge lit up with the French flag colours tonight.
Fergal Keane, BBC News, Marseille
@fergalkeane
tweets: 1/2 Muslim woman in Marseilles tells me: "I am against this terrorist attack but I have also the right to have my free speech
2/2 "...and say that I am not Charlie. I am a Muslim citizen of France."
Rosie Komadina
@TziganaRose
tweets: Loving the spirit of unity right now at The Grand Synagogue in France! #JesuisCharlie".
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Israeli Prime Minister Benjamin Netanyahu and French Prime Minister Manuel Valls are also at the Grand Synagogue of Paris, taking part in a remembrance ceremony along with President Francois Hollande.
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What are the roots of the battle for freedom of speech? Historian Tom Holland, who tweeted out one of Charlie Hebdo cartoons in the wake of Wednesday's attack, explains the ramifications.
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German ministers have accused the anti-immigration movement Pegida of exploiting the Paris attacks.
German Justice Minister Heiko Maas has urged Pegida to call off its next march, scheduled for Monday in the eastern city of Dresden. Last week, 18,000 people turned out for the rally.
"If the organisers had a shred of decency, they would simply cancel these demonstrations," the Bild newspaper quoted him as saying in its issue to be published Monday.
"The victims (of the Paris attacks) do not deserve to be abused by rabble-rousers like these," he said.
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President Francois Hollande is taking part in a remembrance ceremony at the Grand Synagogue of Paris for the victims of the past days' shootings.
Hugh Schofield, BBC News, Paris
The urge is to come back onto the streets and to reclaim the land.
That is what it has felt like through the extraordinary scenes of Sunday.
People have made the comparison with the Liberation demos in 1944, and it is apt.
It is apt not just in terms of numbers, but also in how at that moment, too, French men and women were putting down a marker: France is ours.
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In the Canadian city of Montreal, about 25,000 rallied in support of the Paris attack victims.
The Montreal Canadiens hockey team paid their own tribute by playing the French national anthem, the Marseillaise, before their game on Saturday against the Pittsburgh Penguins.
Reporters without Borders
has strongly criticised the participationof leaders of countries where freedom of expression is restricted.
In a statement, it says it is "appalled by the presence of leaders from countries where journalists and bloggers are systematically persecuted such as Egypt (which is ranked 159th out of 180 countries in RWB's press freedom index), Russia (148th), Turkey (154th) and United Arab Emirates (118th)."
Reporters Without Borders secretary-general Christophe Deloire said, "We must not let predators of press freedom spit on the graves of Charlie Hebdo."
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Kato Zlato
tweets: Four hours of walking and standing in a crowd, we finally made it...to the place where the rally started at 15h #UnityRally
Alison Culliford
Journalist, The Africa Report
emails from Place de la Republique: What has marked me most is to see black, white and Arab people, adults and children, on the Republique statue. Tricolores linked with the Turkish flag, and this right beside the Kurdish flag of those who still seek answers about the women activists killed in this quarter of Paris. I turn round and I see two orthodox Jews, rarely seen in this quarter. It's not about flags or badges of identity but this particular moment still spoke volumes about what France is and what France feels right now.
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Lydia Vassallo, marching in Paris, tells the BBC: "We cannot sit at home and do nothing. I've been here since 2pm and plan to stay until the end.
"I am here because I don't believe that people who are doing their job should get killed in the way that they did and to support France and the people living here.
"I hope this rally will bring hope to people and comfort to the families of the those killed and show the world we need to stay united against this crime."
Peter Miller
emails: It feels as if all of Paris is in the streets. We are still 1km away from Place de la Republique but the street is full of people. It is important the whole of society unites together now in solidarity for the freedom of speech and against hatred that wants to divide us.
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Tighter controls on internet use are likely in the wake of the attacks. European, US and Canadian foreign ministers met ahead of the rally and issued a joint statement.
They say it is essential for major internet providers to co-operate with governments and, if asked, remove online content "that aims to incite hatred and terror".
They also want greater monitoring of the EU's external borders, and are calling for changes to rules on freedom of movement to share information and carry out checks on passengers.
John Burgoine
tweets: @BBC_HaveYourSay It's a refreshing change to see the humanity, unity and love at the march in Paris. Je suis Charlie.
This is the scene on the Boulevard Voltaire as darkness begins to fall on Paris: thousands are making their way to the end point of the demonstration, in the Place de la Nation.
Luci Bonnor, BBC News, Paris
Police vans arrive in Place de la Republique and are applauded. I have never seen this before at a march or demonstration.
Author Stephen Marche
@StephenMarche
tweets: Most French thing ever to happen? "I'm marching but I'm conscious of the confusion and hypocrisy of the situation."
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UK Chief Rabbi Ephraim Mirvis
@chiefrabbi
tweets this picture of himself during the rally, with the text: "Marching together in #france united in support of freedom and democracy and in defiance of terror."
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Thousands attended a demonstration in the French port city of Marseille, a stronghold of the anti-immigration Front National party.
This woman was one of thousands who displayed the slogan "Je suis Charlie" during the rally.
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As darkness descends on Paris, demonstrators continue to inch towards the Place de la Nation in good spirits and in huge numbers.
Malcolm Senior, BBC News, Paris
says the crowds are thinning out at the Place de la Republique, and it is now much easier to cross the square.
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Tower Bridge was among the landmarks in London that were lit to show solidarity with the people of Paris
Isabel Skierka
tweets: Hundreds of #Berlin solidarity demonstrators gather at French embassy, Brandenburger Tor #jesuischarlie
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Sunday's march was "unprecedented" in scale, the French interior ministry has told AFP news agency, making it impossible to count the numbers taking part.
"Demonstrators dispersed around a much wider perimeter than originally predicted," the ministry is quoted as saying.
EJ Philby, Lille, France
emails: There was a smaller, more impromptu rally in downtown Lille. Perhaps a couple hundred people on motorcycles gathered, revving their engines and honking horns at passing cars and people. There were many people who were wearing custom-made jackets sporting the phrase "Je suis Charlie". In the midst of all of this noise, suddenly everyone grew quiet and raised their helmets, remaining completely silent for a full 60 seconds.
Reporters Without Borders
blog: On what grounds are representatives of regimes that are predators of press freedom coming to Paris to pay tribute to Charlie Hebdo, a publication that has always defended the most radical concept of freedom of expression?
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Players from Lyon and Toulouse observed a minute's silence prior to their French Ligue 1 match on Sunday.
Patrick Jackson, BBC News, Paris
Marchers are filtering down side streets to reach Place de la Nation for the final rally.
They are streaming past the cafe where I'm working, wrapped against the chill as the sun goes down, but so many faces beaming with pride, voices still not too hoarse for another yell of "Charlie!" Their hands must be sore from clapping.
"This is serious, this was an attack on freedom, we cannot allow this," says Laurent, who took two hours with his wife Isabelle and daughter Coline to cover 2km.
"We had to get into the streets to show we are not afraid," adds Isabelle.
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British Prime Minister David Cameron has said he attended today's mass rally in Paris to show "solidarity"' with France.
Mr Cameron told the BBC: "It was a demonstration of solidarity, people throughout this country, young and old, black and white, saying we stand with the victims, we are not going to put up with this because we are a free, open, tolerant country. As a Briton I felt that exactly the same."
But he said "we cannot be certain" a Paris-style attack would not happen in the UK. "We live in a free and open democracy. You cannot be certain of always preventing attacks like these from taking place."
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Demonstrators in Berlin gathered around the Brandenburg Gate. Their placards bear a quotation from French novelist Victor Hugo: "Freedom begins where ignorance ends".
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BBC reporter Nick Eardley reports that there were cheers from the crowd as the French flag was projected onto the front of the National Gallery in London's Trafalgar Square.
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Here are demonstrators in Bordeaux, who helped make up the one million marchers in France outside of Paris.
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Our reporter Nick Eardley has sent this picture of the fountain in Trafalgar Square lit red, white and blue as a show of solidarity with France.
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In central London, demonstrators filled Trafalgar Square.
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Outside Paris, at least a million people have attended rallies in France today, according to the AFP news agency.
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President Hollande has met the family of Ahmed Merabet, the police officer who was killed outside the offices of Charlie Hebdo, AFP news agency reports.
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Our colleagues at BBC Monitoring report that Egypt's private ON TV has aired live footage of people visiting the French embassy in Cairo to offer condolences over the victims of the attacks in France.
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In Vienna, thousands joined a demonstration in front of the Austrian chancellor's office for the victims of the French attacks.
Kuzak Ahmed
emails: I am a Nigerian. I feel a strong connection to the chains of events in Paris. I understand what it is to be attacked by religious fundamentalists who care less about human life and have no respect/regard for the freedom of expression. I wish that the French people can overcome the attack on its people.
20 Minutes
French news website
tweets: Republican March: More than 100,000 people in Bordeaux according to first estimates.
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BBC presenter Tim Willcox reports that crowds slowly walking along the Boulevard Voltaire are "going wild" as they show their appreciation for a police marksman who saluted them from the roof of one of the buildings that line the street.
Fran Blandy
France Correspondent, AFP
tweets: Netanyahu looked really uncomfortable, nervously glancing around with 2 bodyguards holding onto him, in world leader march.
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Among those joining the solidarity march in Brussels is Belgian cartoonist Philippe Geluck. Four cartoonists at Charlie Hebdo were killed in the attack on their offices on Wednesday.
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BBC reporter Patrick Jackson sent these pictures back of demonstrators at the Paris rally.
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This image from the air gives some idea of the crowds around the Place de la Republique.
Andrew McKay, Oxford UK
emails: 'L'amour plus fort que la haine' event in solidarity with those who suffered in the French attacks this week, and a reassertion of belief in free speech in Oxford UK, today.
Andre McKayCopyright: Andre McKay
Andre McKayImage caption: Andre McKay
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Henry Slade
emails: World leaders, pathetic. Anyone can get on a plane (paid for by the taxpayer) and walk down the street. They will all be in the office on Monday morning and do nothing about this problem. They just put on a show for the media.
Eric Randolph
AFP journalist in Paris
tweets: Up to 1.5 million at Paris march against terrorism: organiser @AFP
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UK Deputy Prime Minister Nick Clegg has arrived at the rally in London's Trafalgar Square.
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As the crowd of demonstrators inch slowly forward, they continue to chant their support for Charlie Hebdo.
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BBC presenter Mishal Husain, who is in Paris, says many of the banners and placards carried by the demonstrators are expressing messages of love and unity.
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Here's a picture of President Hollande comforting Charlie Hebdo columnist Patrick Pelloux during the march.
Richard Hall
Senior Correspondent, Middle East, Africa Editor, Global Post
tweets: Spoke to Saudi ambassador at #jesuischarlie rally. Says he's here in solidarity with French people. And free speech? No comment.
Elise Barthet
Journalist who tweeted pictures from the initial attack
Elise BarthetCopyright: Elise Barthet
tweets: We finally found a use for decorative pencils #MarchRepublicaine
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People held up pens in front of the French embassy in Berlin, which was illuminated with a sign saying "Je suis Charlie" (I am Charlie) in tribute to those who were killed in Wednesday's massacre.
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The world leaders who took part in the march have arrived back at the Elysee Palace, AFP news agency reports.
They include French President Francois Hollande, German Chancellor Angela Merkel and British Prime Minister David Cameron.
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Joining those who have condemned the attack on Charlie Hebdo is Queen Rania of Jordan.
She wrote on her Facebook page: "This is not about Islam or being offended by the Charlie Hebdo magazine. This is about a handful of extremists who wanted to slaughter people for any reason and at any cost," adding that the attack did not represent Islam, "a religion of peace, tolerance and mercy".
Lada Hinyrj
emails: There is a disconcerting irony in Russian Foreign Minister Sergei Lavrov attending the rally in Paris today when freedom of speech is so curtailed, not permitted and replaced by fantastical propaganda in Russia.
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Overseeing the security of those taking part in the rally in Paris are 2,000 police officers and more than 1,000 soldiers - including elite marksmen on rooftops.
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A reminder that earlier on Sunday a video emerged, purporting to show the gunman who attacked a kosher supermarket in Paris emerged on the internet.
Leaders at the front of the march include Palestinian Authority President Mahmoud Abbas, below right, and Israel's Prime Minister Benjamin Netanyahu, pictured in the lower image.
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The crowds continue to break spontaneously into applause as they march to the Place de la Nation.
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Demonstrators in Paris have been making their way along the Boulevard Voltaire.
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At the gathering at Trafalgar Square in London Avi Gelley, who is Jewish, told the BBC about how "scary" it was to see the attacks in France and said he feels "not safe at all" in London now.
But if we do not stand together against such attacks, he said, "it's only going to get worse".
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Naima Zouhali-Worrall, Paris
emails: It is important for me to take part. I am Moroccan and I have a lot of French friends. When something like this happens, people say, where are the Muslims? Today I am marching and I say that I am Moroccan and I am Charlie.'
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Some of those attending the rally in Paris have explained to BBC correspondent Lyse Doucet why they decided to march.
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By Nick Eardley, BBC News, at Trafalgar Square
There is a sombre but defiant mood in London's Trafalgar Square.
Francois Thaury, 58, is originally from France but has lived in London for 15 years.
"I had to be here today," he said. "As a half-French, half-English citizen, it is so comforting to feel such solidarity from English people."
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One of the leaders of France's Muslims, Mohammad Moussaoui - the head of the Union of French Mosques - has called on all French Muslims to take part in the rally, saying that the attack against Charlie Hebdo was an attack "against France and the French" and that Muslims were also part of this community.
He made the call earlier today in an interview with the French radio station RTL, BBC Monitoring reports.
James Longman, BBC Foreign News Journalist
@JamesAALongman
tweets: 3 people made the world seem very bleak this week. Thousands have restored a little faith #ParisMarch pic RT @BBCNews
James LongmanCopyright: James Longman
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Among the most powerful symbols held by the crowds in Paris are the pencils representing Charlie Hebdo and freedom of expression.
Queen Rania of Jordan
@QueenRania
tweets: There is no justification for responding to an offence with murder. Not in the name of religion. Not in the name of Islam. #ParisShooting
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London is one of many cities around the world holding rallies as a show of support for the march in Paris.
One Parisian who now lives in London, Mathieu Gillet, was at the Trafalgar Square event and he told the BBC: "I'm here to demonstrate that the three values of France - liberty, equality, fraternity - are still alive and we definitely have to fight for those values.
"It's a strong message that people are standing shoulder to shoulder and together, from around the world."
Fergal Keane, BBC Foreign Correspondent
@fergalkeane47
tweets: Michele Teboul, a leading Jewish figure in Marseilles, tells me: "There's real fear... all people are talking about is leaving."
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Demonstrations of support are being held in cities across Europe. These Muslim women took to the streets of Madrid to denounce extremism.
AFPCopyright: AFP
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Haaretz
@harretzcom
tweets: French Jewish and Muslim leaders shake hands in Paris unity rally http://htz.li/1mf #ParisAttacks
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Here's UK Prime Minister David Cameron in line with fellow leaders.
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This picture shows the sheer number of people who gathered in the Place de la Republique.
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We've just received this picture from BBC Europe correspondent Chris Morris in Paris, where a man has clambered on top of a bus stop and unfurled a banner reading "I'm a Muslim not a terrorist" - to applause from the passing crowds.
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James Longman, BBC Foreign News Journalist
@JamesAALongman
tweets: French PM @manuelvalls has tweeted name of each victim one every minute #ParisAttack #ParisMarch #CharieHebdo
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French politicians and Muslim leaders join the march.
AFPCopyright: AFP
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The pan-Arab satellite TV channel Al-Jazeera devoted most of its main morning news bulletin to the Paris rally.
The channel highlighted the presence of political leaders from more than 50 countries, and noted the participation of large numbers of French Muslims, BBC Monitoring reports.
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Here's a closer shot of French President Francois Hollande and Germany's Angela Merkel leading the march with counterparts from around the world.
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Here's another picture of the world leaders taking part in the march, including French President Francois Hollande, German Chancellor Angela Merkel and British Prime Minister David Cameron.
Coralie Diatkine
emails: I am not very optimistic about what this rally will achieve but it has to be done. I am French and republican and an atheist but I feel solidarity with all the victims. I hope to see as many different people as possible at this march. The idea of the republic is that we guarantee freedom for everyone. That is what makes it possible for people not just to co-exist but to mix. French society has been threatened at its core, its cohesion. It is important that we don't give any credit to the different types of terrorism that people want to infuse in our society.
Malcom Senior, BBC News, Paris
A security guard tells me the queue for people wanting to take part in the march stretches back from the place de la Republique to the Gare du Nord, a distance of about two miles.
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Meanwhile, here's another picture of the gathering in Trafalgar Square, London, taken by BBC reporter Nick Eardley.
BreakingBreaking News
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The 40 world leaders attending the rally have assembled and begun the march.
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Malcolm Senior
BBC News, Paris
Thousands and thousands of people, babies in pushchairs, people walking with crutches, young families, couples, all colours filling the Place de la Republique from all the feeder streets, as far as the eye can see.
People chanting "Liberte!" and "Charlie!", pausing only to take photos of the posters commemorating the victims of the killings, the tricolores waving and demonstrators who have climbed the statue of Marianne in the centre of the square.
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Many of the demonstrators in Paris have held pencils as a tribute to those killed at the offices of Charlie Hebdo. This man's sign says "All Live Together".
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Nicolas Henin, a French journalist who was held hostage by Islamic State in Syria and released in April, is among those attending the march.
"Every time that people want to hurt you, the only way you can react, the only decent way, is to show that we are stronger than them," he told the BBC.
Phoebe Frieze, Producer BBC 5Live
@PhoebeFrieze
tweets: Flags adorn the main statue as crowds and media get ready on #PlaceDeLaRepublique for the #UnityMarch in Paris
Phoebe FriezeCopyright: Phoebe Frieze
Mishal Husain
@MishalHusainBBC
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tweets this picture of the crowds filling the Place de la Republique and surrounding streets.
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In Paris's Place de la Republique those who have gathered are singing the national anthem and breaking out into spontaneous cheers and applause.
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Fergal Keane
BBC News, Marseille
Thousands of people are marching in Marseille, the city with France's largest Muslim population in France.
The mayor of the city's Quartiers Nord district, Samia Ghali, a Muslim of Algerian descent, told the BBC people were marching for tolerance and co-existence.
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BBC reporter Nick Eardley sent this picture of the gathering in Trafalgar Square in London.
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Italian Prime Minister Matteo Renzi has just spoken live to BBC television news.
"This is a very important event because for the first time we give the message Europe will be the place for the future, not only the place that has given freedom for 70 years," he said. "If terrorism tries to destroy our values the answer will come altogether.
"I represent my people but I am also a part of the European people. This is a moment of solidarity, but also of hope."
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President Hollande is now leaving the Elysee Palace to go to the march.
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Tributes have been left at the French Embassy in London, as the English capital prepares to pay tribute to the victims by turning some of its most famous landmarks red, white and blue.
Giksy
@g1k5y
tweets: Surreal scenes in Paris: entire streets are blocked to cars and really crowded with people wishing to join the walk... Heavy police presence in the streets and we can hardly join the walk as international heads of state are there
Chris Morris, Europe Correspondent, BBC News
@BBCChrisMorris
tweets: All of French life seems to be here - old & young; black & white; left & right; flags, slogans, chanting and applause
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"The importance of today is to show solidarity with the French people and the French government after the appalling attacks in Paris," UK Prime Minister David Cameron told the BBC News Channel in an interview from Paris.
"We're here to demonstrate that we all stand for values of democracy, of freedom, of freedom of expression, of tolerance. But there's also something else - which is that we in Britain face a very similar threat, a threat of fanatical extremism and we have to confront that in every way we can."
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Managing a gathering of this size is a phenomenal logistical exercise. Here are the two routes the march will be taking through Paris.
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Chris Moos
@ChrisMoos_
tweets: Great response on #CharlieHebdo from a child: "When I grow up, I'll be a journalist. I'm not afraid." #JeSuisCharlie
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AFP news agency is reporting that the four Jewish civilians killed in the kosher supermarket on Friday will be buried together in Israel on Tuesday.
Lyse Doucet, BBC Presenter and Chief International Correspondent
@bbclysedoucet
tweets: What was for days a sad & silent Place de la Republique is today alive with a loud statement for unity, against terrorism
Mishal Husain, BBC News presenter
@MishalHusainBBC
Mishal HusainCopyright: Mishal Husain
tweets: Place de la Republique ahead of the march #jesuischarlie
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The BBC's Patrick Jackson has been gauging the response to the attacks from people in the French capital.
"Freedom and freedom of speech, which are essential to a democracy, have been put into question by this disaster," says one man.
A human tide is flowing steadily along streets shut to traffic into the Place de la Republique, says the BBC's Patrick Jackson at the scene.
Everywhere is the slogan "Je suis Charlie" ("I am Charlie"): on homemade placards, on armbands, on T-shirts. A family marches four abreast holding up print-outs in plastic sleeves.
And there are flags too: full-sized French tricolores carried by demonstrators, the colours of the Republic on the Square of the Republic.
They are waved from the tiers of the iconic Republic monument, where demonstrators are perched on the giant statues symbolising the old, but so vital for this nation now, values of liberty, equality and fraternity.
Imelda Flattery, BBC News, Senior Europe Producer.
@Imeldaflattery
tweets: Streets around Place De La Republic backed up as far as you can see.
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Israel's Prime Minister Benjamin Netanyahu is among the world leaders attending the march.
Marianne Barriaux, AFP France correspondent
@MBarriaux
tweets: Thousands shouting 'Charlie', 'Charlie' at Place de la Republique in Paris @AFP #CharlieHebdo
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In the aftermath of this week's attacks, the US will host a summit on combating "violent extremism around the world", Attorney General Eric Holder has said.
The meeting in Washington on 18 February would also aim to "pool our resources".
Damian Grammaticas, BBC Europe Correspondent
@dngbbc
tweets: French Presidents and Prime Ministers past and present united today #CharlieHebdo #Marcherepublicaine
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British Prime Minister David Cameron met French President Francois Hollande at the Elysee Palace ahead of the march.
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The families of those killed in the Charlie Hebdo attack have arrived for this afternoon's march.
Twelve people were killed in Wednesday's attack on the satirical magazine.
They will be joined by dignitaries including the British, German and Israeli leaders as well as Russian Foreign Minister Sergei Lavrov and Turkish Prime Minister Ahmet Davutoglu.
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Hundreds of thousands of people have gathered on the Place de la Republique.
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Palestinian president Mahmoud Abbas was among the leaders to have been welcomed to the Elysee Palace by French President Francois Hollande.
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Meanwhile, in east London street artists have put up this tribute to those murdered at Charlie Hebdo.
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Solidarity demonstrations are taking place across Europe, including this one in Madrid, where marchers are holding placards reading, "We are all Charlie".
Get involved
Email talkingpoint@bbc.co.uk
Jon Foster emails: I am an English lawyer living in Paris. In standing up for the freedom of speech, let us remember the difference between satire (and that there is no right not to be offended) and hate speech (to which the European Court of Human Rights has held there is no right).
Let us also not forget the two Muslim heroes, Ahmed Merabet, the policeman who died so horribly in defending Charlie Hebdo's right to ridicule his faith; and Lassana Bathily, who acted so bravely to protect the Jewish customers of the kosher supermarket. These men deserve the strongest recognition as living up to to Voltarian values of the Republic.
Get involved
Email talkingpoint@bbc.co.uk
Euan Wall emails: I am a British student studying at the Sorbonne in Paris. Despite this being exams week, and having three exams in the next two days, my fellow students and I are taking to the streets in Paris to try and show that despite the current political atmosphere, France can unite around ideas like freedom of expression and rejection of barbarity.
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Paris prosecutors are linking the shooting of a jogger to Amedy Coulibaly, the gunman who also murdered a policewoman and four hostages at a kosher supermarket.
The jogger was shot and injured in a Paris suburb on Wednesday, the same day as the Charlie Hebdo massacre, and two days before the supermarket hostage-taking.
The prosecutor said ballistics tests on shell cases from the shooting in Fontenay-aux Roses linked them to the automatic weapon at the kosher store.
Coulibaly and his partner lived in Fontenay-aux-Roses.
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The BBC's James Longman tweets this picture of one demonstrator, called Patrice, who says he's "proud to be here".
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The controversial French comic Dieudonne M'bala M'bala, whose anti-Semitic remarks have in the past sparked a row over the acceptable limits of free speech, tweets: "Attending the march alongside the defenders of freedom of expression. Thoughts for all those who have never been afraid to die laughing."
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More than a million people are expected to attend this afternoon's march. Check out some of the latest pictures from Paris in our picture gallery.
Getty ImagesCopyright: Getty Images
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There have been a number of tales of heroism during the attacks.
BBC journalist Imelda Flattery tweets from Paris: "Rail tickets to Paris from Brussels, Amsterdam and Cologne reduced for the day to 29 euros for the Paris March."
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UK Chief Rabbi Ephraim Mirvis arrives for the Paris march and tells the BBC he's been "saddened and anxious" but that Sunday is about "solidarity with France".
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Earlier on Sunday there was an arson attack at the offices of a German newspaper that reprinted the Charlie Hebdo cartoons of the Prophet Muhammad.
No-one was hurt in the assault on the Hamburger Morgenpost. Two men have been arrested.
APCopyright: AP
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Belgium's interior minister Jan Jambon is calling for a EU list of "foreign fighters" to be set up. In a tweet (in French), he says "co-operation between intelligence services is vital".
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A jarring note is sounded by two prominent Russian politicians, who criticise Ukrainian President Petro Poroshenko for attending today's march in Paris.
The chairman of the Russian parliament's committee for International Affairs, Alexey Pushkov, tweets sarcastically that Poroshenko is attending a march against terrorism, but has failed to take tough action against those responsible for an "act of terrorism" in the southern Ukrainian city of Odessa.
Nationalist politician Eduard Limonov writes on the blogging platform LiveJournal that if Poroshenko, "who ordered the shelling of the peaceful city of Donbass", can take part in the Paris march, then the event is "worthless".
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Valerie Moreau emails: Hello, I'm French, I'm Parisian and I'm Charlie. I'd like to thank all the people all over the world for being beside us in these terrible days. As murderers try to put us in the dark, all of you and all of us are the lights that won't extinguish. It's really comforting to feel all of you beside us. Thank you, thank you, thank you.
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People gathered in the main square of the village of Dammartin-en-Goele, the village north of Paris where the Charlie Hebdo gunmen , Said and Cherif Kouachi, were both shot dead by police.
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Check out the BBC Arabic's bird's-eye view from a balcony overlooking Boulevard Voltaire, which people will pass through to reach the starting point of the march at Place de la Republique.
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Spain's interior minister says he will call for border controls to be re-established between many EU countries in order to stop jihadists returning from the Middle East.
Interior Minister Jorge Fernandez Diaz told the newspaper El Pais (in Spanish) that it may be necessary to modify the Schengen treaty, which abolished border checks between 26 European countries.
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About 2,000 police officers have been deployed to protect those at the rally. The security presence has been bolstered by 1,350 soldiers - including elite marksmen on rooftops.
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People bearing French flags and tributes to those killed are among tens of thousands of demonstrators gathering in the Place de la Republique, two hours before the march is scheduled to begin.
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Police in France are still hunting for accomplices of those behind this week's terror attacks.
Among those being hunted is Hayat Boumeddiene, the partner of the gunman who attacked a kosher supermarket on Friday.
The attacks in France have led to soul-searching in other countries. In Britain, the former head of the British Royal Navy, Lord West, warned against a knee-jerk reaction.
"It's a serious threat, but I would say it's the ideal time to be British and have a stiff upper lip and just step back and be calm…" the Labour peer told the BBC.
"This was a horrible incident by murdering, murderous people [but] there is a threat that could happen [here]. We mustn't kid ourselves. They only need to be lucky once, as was famously said once, whereas we have got to be lucky all the time."
Sara Firth, Correspondent & Photojournalist, Huffington Post
@Sara__Firth
tweets: The message from many turning out to attend the #Paris #UnityMarch today. #NotAfraid pic.twitter.com/dXsr77WUKF
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French President Francois Hollande will visit the main synagogue in Paris, the Grande Synagogue, after the rally, BFMTV reports, quoting a source in the Elysee Palace. The French paper Le Point carries a similar report, and adds that a ceremony will be held at the synagogue in commemoration of all the victims.
The city's mayor, Boris Johnson, says Londoners have been "appalled" at the attacks, and it was important to "demonstrate our solidarity with the people of Paris".
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Interior ministers from across the world have been holding talks in Paris ahead of this afternoon's march.
French Interior Minister Bernard Cazeneuve says that while it is an informal group, it will lead to concrete action within the European Union. The president of Latvia will host another gathering in coming days.
"The whole of France is in mourning; it is the values of Europe - democracy - that these terrorists wanted to attack," he said.
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Meanwhile, that crowd in the Place de la Republique is swelling. They are chanting "Liberte! Liberte! Charlie! Charlie!" and singing the Marseillaise.
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British Prime Minister David Cameron has tweeted: I'm on my way to Paris to march with the French people. The #CharlieHebdo murders will not crush our spirit or our values.
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Across the border in Germany, police in the northern city of Hamburg have arrested two men on suspicion of carrying out an arson attack against a newspaper which republished cartoons from Charlie Hebdo.
Rocks and a burning object were thrown through the window of the offices of the Hamburger Morgenpost early on Sunday.
Two rooms on the lower floors were damaged but the fire was quickly extinguished and no-one was hurt.
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Crowds are already gathering in Paris' Place de la Republique ahead of this afternoon's march.
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French President Francois Hollande has reassured the country's Jewish community that they will be protected in the wake of Coulibaly's attack on the kosher supermarket which left four people dead.
He made the assurance at a meeting with Jewish leaders at the Elysee Palace. One of those who attended said new security measures to protect synagogues and Jewish institutions would be put in place from today.
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AFPCopyright: AFP
Text accompanying the video says Coulibaly was behind the deaths of a policewoman and "five Jews", also claiming he had planted a bomb on a car in Paris.
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The seven-minute, slickly edited video shows Coulibaly variously doing press-ups, dressed in robes, and displaying an array of automatic weapons and handguns.
Asked whether he has links with the Charlie Hebdo killers, Cherif and Said Kouachi, he says: "The brothers of our team were split into two groups… I went out a bit against the police.
"If we did things a bit together and a bit separately, it was to have more impact."
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A video has emerged in which Coulibaly, who also reportedly shot dead a policewoman on Thursday, claims to be acting on behalf of Islamic State (IS). In the video, he pledges his allegiance to Caliph Ibrahim al-Baghdadi, the head of IS, and says he was co-ordinating his attacks with the two brothers who attacked the Charlie Hebdo offices on Wednesday.
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Hayat Boumeddiene, the partner of Amedy Coulibaly - who attacked a kosher supermarket in eastern Paris on Friday, killing four hostages and taking hostages before being killed by police - is still wanted by police. She is thought to have fled France last week.
Officials believe she may have entered Turkey en route to Syria.
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Meanwhile, French police are still seeking accomplices of the gunmen who attacked satirical magazine Charlie Hebdo and a kosher supermarket.
Eleven people were killed at the magazine offices in Paris on Wednesday, with a policeman shot dead nearby. Four hostages died at the supermarket on Friday.
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About 2,000 police officers and 1,350 soldiers are being deployed in Paris to protect more than a million marchers.
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We'll be bringing you all the latest news from the French capital, where huge crowds and some 40 world leaders are expected later for a massive unity rally through the city.
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Hello and welcome to our coverage of events in Paris, still reeling from three days of terror attacks this week which killed 17 people.
Live Reporting
Michael Hirst, Keith Moore, Alix Kroeger and Kerry Alexandra
All times stated are UK
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Latest PostPost update
And that concludes our live coverage of Sunday's march in Paris in support of unity and the victims of last week's attacks, in which 17 people were killed. The French interior ministry has said it was the biggest demonstration in French history.
President Francois Hollande was joined by 40 world leaders who linked arms at the start of the marches. He said Paris was the capital of the world for the day.
There were also rallies in other French cities, across Europe, and around the world, from Beirut to Montreal.
You can follow further updates, as well as background material on the story, on the BBC News website.
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"The (French) Jewish community is in need of reassurance... Each new tragedy has the Jewish community more and more worried," Jack-Ivey Bohbot told BFMTV.
Imelda Flattery, BBC News
@ImeldaFlattery
tweets: London's Tower Bridge lit up with the French flag colours tonight.
Fergal Keane, BBC News, Marseille
@fergalkeane
tweets: 1/2 Muslim woman in Marseilles tells me: "I am against this terrorist attack but I have also the right to have my free speech
2/2 "...and say that I am not Charlie. I am a Muslim citizen of France."
Rosie Komadina
@TziganaRose
tweets: Loving the spirit of unity right now at The Grand Synagogue in France! #JesuisCharlie".
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Israeli Prime Minister Benjamin Netanyahu and French Prime Minister Manuel Valls are also at the Grand Synagogue of Paris, taking part in a remembrance ceremony along with President Francois Hollande.
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What are the roots of the battle for freedom of speech? Historian Tom Holland, who tweeted out one of Charlie Hebdo cartoons in the wake of Wednesday's attack, explains the ramifications.
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German ministers have accused the anti-immigration movement Pegida of exploiting the Paris attacks.
German Justice Minister Heiko Maas has urged Pegida to call off its next march, scheduled for Monday in the eastern city of Dresden. Last week, 18,000 people turned out for the rally.
"If the organisers had a shred of decency, they would simply cancel these demonstrations," the Bild newspaper quoted him as saying in its issue to be published Monday.
"The victims (of the Paris attacks) do not deserve to be abused by rabble-rousers like these," he said.
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President Francois Hollande is taking part in a remembrance ceremony at the Grand Synagogue of Paris for the victims of the past days' shootings.
Hugh Schofield, BBC News, Paris
The urge is to come back onto the streets and to reclaim the land.
That is what it has felt like through the extraordinary scenes of Sunday.
People have made the comparison with the Liberation demos in 1944, and it is apt.
It is apt not just in terms of numbers, but also in how at that moment, too, French men and women were putting down a marker: France is ours.
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In the Canadian city of Montreal, about 25,000 rallied in support of the Paris attack victims.
The Montreal Canadiens hockey team paid their own tribute by playing the French national anthem, the Marseillaise, before their game on Saturday against the Pittsburgh Penguins.
Reporters without Borders
has strongly criticised the participationof leaders of countries where freedom of expression is restricted.
In a statement, it says it is "appalled by the presence of leaders from countries where journalists and bloggers are systematically persecuted such as Egypt (which is ranked 159th out of 180 countries in RWB's press freedom index), Russia (148th), Turkey (154th) and United Arab Emirates (118th)."
Reporters Without Borders secretary-general Christophe Deloire said, "We must not let predators of press freedom spit on the graves of Charlie Hebdo."
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Kato Zlato
tweets: Four hours of walking and standing in a crowd, we finally made it...to the place where the rally started at 15h #UnityRally
Alison Culliford
Journalist, The Africa Report
emails from Place de la Republique: What has marked me most is to see black, white and Arab people, adults and children, on the Republique statue. Tricolores linked with the Turkish flag, and this right beside the Kurdish flag of those who still seek answers about the women activists killed in this quarter of Paris. I turn round and I see two orthodox Jews, rarely seen in this quarter. It's not about flags or badges of identity but this particular moment still spoke volumes about what France is and what France feels right now.
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Lydia Vassallo, marching in Paris, tells the BBC: "We cannot sit at home and do nothing. I've been here since 2pm and plan to stay until the end.
"I am here because I don't believe that people who are doing their job should get killed in the way that they did and to support France and the people living here.
"I hope this rally will bring hope to people and comfort to the families of the those killed and show the world we need to stay united against this crime."
Peter Miller
emails: It feels as if all of Paris is in the streets. We are still 1km away from Place de la Republique but the street is full of people. It is important the whole of society unites together now in solidarity for the freedom of speech and against hatred that wants to divide us.
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Tighter controls on internet use are likely in the wake of the attacks. European, US and Canadian foreign ministers met ahead of the rally and issued a joint statement.
They say it is essential for major internet providers to co-operate with governments and, if asked, remove online content "that aims to incite hatred and terror".
They also want greater monitoring of the EU's external borders, and are calling for changes to rules on freedom of movement to share information and carry out checks on passengers.
John Burgoine
tweets: @BBC_HaveYourSay It's a refreshing change to see the humanity, unity and love at the march in Paris. Je suis Charlie.
Silvia Costeloe, BBC News
tweets from central London: CharlieHebdo memorial in Trafalgar square #JeSuisCharlie #JeSuisAhmed
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This is the scene on the Boulevard Voltaire as darkness begins to fall on Paris: thousands are making their way to the end point of the demonstration, in the Place de la Nation.
Luci Bonnor, BBC News, Paris
Police vans arrive in Place de la Republique and are applauded. I have never seen this before at a march or demonstration.
Author Stephen Marche
@StephenMarche
tweets: Most French thing ever to happen? "I'm marching but I'm conscious of the confusion and hypocrisy of the situation."
UK Chief Rabbi Ephraim Mirvis
@chiefrabbi
tweets this picture of himself during the rally, with the text: "Marching together in #france united in support of freedom and democracy and in defiance of terror."
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Thousands attended a demonstration in the French port city of Marseille, a stronghold of the anti-immigration Front National party.
Caroline Politi
tweets this image from @Chapo_ad at Place de la Republique.
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This woman was one of thousands who displayed the slogan "Je suis Charlie" during the rally.
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As darkness descends on Paris, demonstrators continue to inch towards the Place de la Nation in good spirits and in huge numbers.
Malcolm Senior, BBC News, Paris
says the crowds are thinning out at the Place de la Republique, and it is now much easier to cross the square.
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Tower Bridge was among the landmarks in London that were lit to show solidarity with the people of Paris
Isabel Skierka
tweets: Hundreds of #Berlin solidarity demonstrators gather at French embassy, Brandenburger Tor #jesuischarlie
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Sunday's march was "unprecedented" in scale, the French interior ministry has told AFP news agency, making it impossible to count the numbers taking part.
"Demonstrators dispersed around a much wider perimeter than originally predicted," the ministry is quoted as saying.
EJ Philby, Lille, France
emails: There was a smaller, more impromptu rally in downtown Lille. Perhaps a couple hundred people on motorcycles gathered, revving their engines and honking horns at passing cars and people. There were many people who were wearing custom-made jackets sporting the phrase "Je suis Charlie". In the midst of all of this noise, suddenly everyone grew quiet and raised their helmets, remaining completely silent for a full 60 seconds.
Reporters Without Borders
blog: On what grounds are representatives of regimes that are predators of press freedom coming to Paris to pay tribute to Charlie Hebdo, a publication that has always defended the most radical concept of freedom of expression?
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Players from Lyon and Toulouse observed a minute's silence prior to their French Ligue 1 match on Sunday.
Patrick Jackson, BBC News, Paris
Marchers are filtering down side streets to reach Place de la Nation for the final rally.
They are streaming past the cafe where I'm working, wrapped against the chill as the sun goes down, but so many faces beaming with pride, voices still not too hoarse for another yell of "Charlie!" Their hands must be sore from clapping.
"This is serious, this was an attack on freedom, we cannot allow this," says Laurent, who took two hours with his wife Isabelle and daughter Coline to cover 2km.
"We had to get into the streets to show we are not afraid," adds Isabelle.
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British Prime Minister David Cameron has said he attended today's mass rally in Paris to show "solidarity"' with France.
Mr Cameron told the BBC: "It was a demonstration of solidarity, people throughout this country, young and old, black and white, saying we stand with the victims, we are not going to put up with this because we are a free, open, tolerant country. As a Briton I felt that exactly the same."
But he said "we cannot be certain" a Paris-style attack would not happen in the UK. "We live in a free and open democracy. You cannot be certain of always preventing attacks like these from taking place."
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Demonstrators in Berlin gathered around the Brandenburg Gate. Their placards bear a quotation from French novelist Victor Hugo: "Freedom begins where ignorance ends".
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BBC reporter Nick Eardley reports that there were cheers from the crowd as the French flag was projected onto the front of the National Gallery in London's Trafalgar Square.
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Here are demonstrators in Bordeaux, who helped make up the one million marchers in France outside of Paris.
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Our reporter Nick Eardley has sent this picture of the fountain in Trafalgar Square lit red, white and blue as a show of solidarity with France.
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In central London, demonstrators filled Trafalgar Square.
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Outside Paris, at least a million people have attended rallies in France today, according to the AFP news agency.
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President Hollande has met the family of Ahmed Merabet, the police officer who was killed outside the offices of Charlie Hebdo, AFP news agency reports.
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Our colleagues at BBC Monitoring report that Egypt's private ON TV has aired live footage of people visiting the French embassy in Cairo to offer condolences over the victims of the attacks in France.
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In Vienna, thousands joined a demonstration in front of the Austrian chancellor's office for the victims of the French attacks.
Kuzak Ahmed
emails: I am a Nigerian. I feel a strong connection to the chains of events in Paris. I understand what it is to be attacked by religious fundamentalists who care less about human life and have no respect/regard for the freedom of expression. I wish that the French people can overcome the attack on its people.
20 Minutes
French news website
tweets: Republican March: More than 100,000 people in Bordeaux according to first estimates.
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BBC presenter Tim Willcox reports that crowds slowly walking along the Boulevard Voltaire are "going wild" as they show their appreciation for a police marksman who saluted them from the roof of one of the buildings that line the street.
Fran Blandy
France Correspondent, AFP
tweets: Netanyahu looked really uncomfortable, nervously glancing around with 2 bodyguards holding onto him, in world leader march.
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Among those joining the solidarity march in Brussels is Belgian cartoonist Philippe Geluck. Four cartoonists at Charlie Hebdo were killed in the attack on their offices on Wednesday.
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BBC reporter Patrick Jackson sent these pictures back of demonstrators at the Paris rally.
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This image from the air gives some idea of the crowds around the Place de la Republique.
Andrew McKay, Oxford UK
emails: 'L'amour plus fort que la haine' event in solidarity with those who suffered in the French attacks this week, and a reassertion of belief in free speech in Oxford UK, today.
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Henry Slade
emails: World leaders, pathetic. Anyone can get on a plane (paid for by the taxpayer) and walk down the street. They will all be in the office on Monday morning and do nothing about this problem. They just put on a show for the media.
Eric Randolph
AFP journalist in Paris
tweets: Up to 1.5 million at Paris march against terrorism: organiser @AFP
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UK Deputy Prime Minister Nick Clegg has arrived at the rally in London's Trafalgar Square.
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As the crowd of demonstrators inch slowly forward, they continue to chant their support for Charlie Hebdo.
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BBC presenter Mishal Husain, who is in Paris, says many of the banners and placards carried by the demonstrators are expressing messages of love and unity.
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Here's a picture of President Hollande comforting Charlie Hebdo columnist Patrick Pelloux during the march.
Richard Hall
Senior Correspondent, Middle East, Africa Editor, Global Post
tweets: Spoke to Saudi ambassador at #jesuischarlie rally. Says he's here in solidarity with French people. And free speech? No comment.
Elise Barthet
Journalist who tweeted pictures from the initial attack
tweets: We finally found a use for decorative pencils #MarchRepublicaine
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People held up pens in front of the French embassy in Berlin, which was illuminated with a sign saying "Je suis Charlie" (I am Charlie) in tribute to those who were killed in Wednesday's massacre.
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The world leaders who took part in the march have arrived back at the Elysee Palace, AFP news agency reports.
They include French President Francois Hollande, German Chancellor Angela Merkel and British Prime Minister David Cameron.
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Joining those who have condemned the attack on Charlie Hebdo is Queen Rania of Jordan.
She wrote on her Facebook page: "This is not about Islam or being offended by the Charlie Hebdo magazine. This is about a handful of extremists who wanted to slaughter people for any reason and at any cost," adding that the attack did not represent Islam, "a religion of peace, tolerance and mercy".
Lada Hinyrj
emails: There is a disconcerting irony in Russian Foreign Minister Sergei Lavrov attending the rally in Paris today when freedom of speech is so curtailed, not permitted and replaced by fantastical propaganda in Russia.
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Overseeing the security of those taking part in the rally in Paris are 2,000 police officers and more than 1,000 soldiers - including elite marksmen on rooftops.
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A reminder that earlier on Sunday a video emerged, purporting to show the gunman who attacked a kosher supermarket in Paris emerged on the internet.
In it, Amedy Coulibaly - who died in the police raid to end the siege - says he carried out the attack on behalf of Islamic State.
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Leaders at the front of the march include Palestinian Authority President Mahmoud Abbas, below right, and Israel's Prime Minister Benjamin Netanyahu, pictured in the lower image.
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The crowds continue to break spontaneously into applause as they march to the Place de la Nation.
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Demonstrators in Paris have been making their way along the Boulevard Voltaire.
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At the gathering at Trafalgar Square in London Avi Gelley, who is Jewish, told the BBC about how "scary" it was to see the attacks in France and said he feels "not safe at all" in London now.
But if we do not stand together against such attacks, he said, "it's only going to get worse".
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Naima Zouhali-Worrall, Paris
emails: It is important for me to take part. I am Moroccan and I have a lot of French friends. When something like this happens, people say, where are the Muslims? Today I am marching and I say that I am Moroccan and I am Charlie.'
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Some of those attending the rally in Paris have explained to BBC correspondent Lyse Doucet why they decided to march.
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By Nick Eardley, BBC News, at Trafalgar Square
There is a sombre but defiant mood in London's Trafalgar Square.
Francois Thaury, 58, is originally from France but has lived in London for 15 years.
"I had to be here today," he said. "As a half-French, half-English citizen, it is so comforting to feel such solidarity from English people."
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One of the leaders of France's Muslims, Mohammad Moussaoui - the head of the Union of French Mosques - has called on all French Muslims to take part in the rally, saying that the attack against Charlie Hebdo was an attack "against France and the French" and that Muslims were also part of this community.
He made the call earlier today in an interview with the French radio station RTL, BBC Monitoring reports.
James Longman, BBC Foreign News Journalist
@JamesAALongman
tweets: 3 people made the world seem very bleak this week. Thousands have restored a little faith #ParisMarch pic RT @BBCNews
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Among the most powerful symbols held by the crowds in Paris are the pencils representing Charlie Hebdo and freedom of expression.
Queen Rania of Jordan
@QueenRania
tweets: There is no justification for responding to an offence with murder. Not in the name of religion. Not in the name of Islam. #ParisShooting
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London is one of many cities around the world holding rallies as a show of support for the march in Paris.
One Parisian who now lives in London, Mathieu Gillet, was at the Trafalgar Square event and he told the BBC: "I'm here to demonstrate that the three values of France - liberty, equality, fraternity - are still alive and we definitely have to fight for those values.
"It's a strong message that people are standing shoulder to shoulder and together, from around the world."
Fergal Keane, BBC Foreign Correspondent
@fergalkeane47
tweets: Michele Teboul, a leading Jewish figure in Marseilles, tells me: "There's real fear... all people are talking about is leaving."
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Demonstrations of support are being held in cities across Europe. These Muslim women took to the streets of Madrid to denounce extremism.
Haaretz
@harretzcom
tweets: French Jewish and Muslim leaders shake hands in Paris unity rally http://htz.li/1mf #ParisAttacks
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Here's UK Prime Minister David Cameron in line with fellow leaders.
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This picture shows the sheer number of people who gathered in the Place de la Republique.
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We've just received this picture from BBC Europe correspondent Chris Morris in Paris, where a man has clambered on top of a bus stop and unfurled a banner reading "I'm a Muslim not a terrorist" - to applause from the passing crowds.
James Longman, BBC Foreign News Journalist
@JamesAALongman
tweets: French PM @manuelvalls has tweeted name of each victim one every minute #ParisAttack #ParisMarch #CharieHebdo
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French politicians and Muslim leaders join the march.
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The pan-Arab satellite TV channel Al-Jazeera devoted most of its main morning news bulletin to the Paris rally.
The channel highlighted the presence of political leaders from more than 50 countries, and noted the participation of large numbers of French Muslims, BBC Monitoring reports.
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Here's a closer shot of French President Francois Hollande and Germany's Angela Merkel leading the march with counterparts from around the world.
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Here's another picture of the world leaders taking part in the march, including French President Francois Hollande, German Chancellor Angela Merkel and British Prime Minister David Cameron.
Coralie Diatkine
emails: I am not very optimistic about what this rally will achieve but it has to be done. I am French and republican and an atheist but I feel solidarity with all the victims. I hope to see as many different people as possible at this march. The idea of the republic is that we guarantee freedom for everyone. That is what makes it possible for people not just to co-exist but to mix. French society has been threatened at its core, its cohesion. It is important that we don't give any credit to the different types of terrorism that people want to infuse in our society.
Malcom Senior, BBC News, Paris
A security guard tells me the queue for people wanting to take part in the march stretches back from the place de la Republique to the Gare du Nord, a distance of about two miles.
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Meanwhile, here's another picture of the gathering in Trafalgar Square, London, taken by BBC reporter Nick Eardley.
BreakingBreaking News
The 40 world leaders attending the rally have assembled and begun the march.
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Malcolm Senior
BBC News, Paris
Thousands and thousands of people, babies in pushchairs, people walking with crutches, young families, couples, all colours filling the Place de la Republique from all the feeder streets, as far as the eye can see.
People chanting "Liberte!" and "Charlie!", pausing only to take photos of the posters commemorating the victims of the killings, the tricolores waving and demonstrators who have climbed the statue of Marianne in the centre of the square.
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Many of the demonstrators in Paris have held pencils as a tribute to those killed at the offices of Charlie Hebdo. This man's sign says "All Live Together".
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Nicolas Henin, a French journalist who was held hostage by Islamic State in Syria and released in April, is among those attending the march.
"Every time that people want to hurt you, the only way you can react, the only decent way, is to show that we are stronger than them," he told the BBC.
Phoebe Frieze, Producer BBC 5Live
@PhoebeFrieze
tweets: Flags adorn the main statue as crowds and media get ready on #PlaceDeLaRepublique for the #UnityMarch in Paris
Mishal Husain
@MishalHusainBBC
tweets this picture of the crowds filling the Place de la Republique and surrounding streets.
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In Paris's Place de la Republique those who have gathered are singing the national anthem and breaking out into spontaneous cheers and applause.
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Fergal Keane
BBC News, Marseille
Thousands of people are marching in Marseille, the city with France's largest Muslim population in France.
The mayor of the city's Quartiers Nord district, Samia Ghali, a Muslim of Algerian descent, told the BBC people were marching for tolerance and co-existence.
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BBC reporter Nick Eardley sent this picture of the gathering in Trafalgar Square in London.
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Italian Prime Minister Matteo Renzi has just spoken live to BBC television news.
"This is a very important event because for the first time we give the message Europe will be the place for the future, not only the place that has given freedom for 70 years," he said. "If terrorism tries to destroy our values the answer will come altogether.
"I represent my people but I am also a part of the European people. This is a moment of solidarity, but also of hope."
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President Hollande is now leaving the Elysee Palace to go to the march.
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Tributes have been left at the French Embassy in London, as the English capital prepares to pay tribute to the victims by turning some of its most famous landmarks red, white and blue.
Giksy
@g1k5y
tweets: Surreal scenes in Paris: entire streets are blocked to cars and really crowded with people wishing to join the walk... Heavy police presence in the streets and we can hardly join the walk as international heads of state are there
Chris Morris, Europe Correspondent, BBC News
@BBCChrisMorris
tweets: All of French life seems to be here - old & young; black & white; left & right; flags, slogans, chanting and applause
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"The importance of today is to show solidarity with the French people and the French government after the appalling attacks in Paris," UK Prime Minister David Cameron told the BBC News Channel in an interview from Paris.
"We're here to demonstrate that we all stand for values of democracy, of freedom, of freedom of expression, of tolerance. But there's also something else - which is that we in Britain face a very similar threat, a threat of fanatical extremism and we have to confront that in every way we can."
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Managing a gathering of this size is a phenomenal logistical exercise. Here are the two routes the march will be taking through Paris.
Chris Moos
@ChrisMoos_
tweets: Great response on #CharlieHebdo from a child: "When I grow up, I'll be a journalist. I'm not afraid." #JeSuisCharlie
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AFP news agency is reporting that the four Jewish civilians killed in the kosher supermarket on Friday will be buried together in Israel on Tuesday.
Lyse Doucet, BBC Presenter and Chief International Correspondent
@bbclysedoucet
tweets: What was for days a sad & silent Place de la Republique is today alive with a loud statement for unity, against terrorism
Mishal Husain, BBC News presenter
@MishalHusainBBC
tweets: Place de la Republique ahead of the march #jesuischarlie
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The BBC's Patrick Jackson has been gauging the response to the attacks from people in the French capital.
"Freedom and freedom of speech, which are essential to a democracy, have been put into question by this disaster," says one man.
Read more reactions here.
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A human tide is flowing steadily along streets shut to traffic into the Place de la Republique, says the BBC's Patrick Jackson at the scene.
Everywhere is the slogan "Je suis Charlie" ("I am Charlie"): on homemade placards, on armbands, on T-shirts. A family marches four abreast holding up print-outs in plastic sleeves.
And there are flags too: full-sized French tricolores carried by demonstrators, the colours of the Republic on the Square of the Republic.
They are waved from the tiers of the iconic Republic monument, where demonstrators are perched on the giant statues symbolising the old, but so vital for this nation now, values of liberty, equality and fraternity.
Imelda Flattery, BBC News, Senior Europe Producer.
@Imeldaflattery
tweets: Streets around Place De La Republic backed up as far as you can see.
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Israel's Prime Minister Benjamin Netanyahu is among the world leaders attending the march.
Marianne Barriaux, AFP France correspondent
@MBarriaux
tweets: Thousands shouting 'Charlie', 'Charlie' at Place de la Republique in Paris @AFP #CharlieHebdo
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In the aftermath of this week's attacks, the US will host a summit on combating "violent extremism around the world", Attorney General Eric Holder has said.
The meeting in Washington on 18 February would also aim to "pool our resources".
Damian Grammaticas, BBC Europe Correspondent
@dngbbc
tweets: French Presidents and Prime Ministers past and present united today #CharlieHebdo #Marcherepublicaine
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British Prime Minister David Cameron met French President Francois Hollande at the Elysee Palace ahead of the march.
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The families of those killed in the Charlie Hebdo attack have arrived for this afternoon's march.
Twelve people were killed in Wednesday's attack on the satirical magazine.
They will be joined by dignitaries including the British, German and Israeli leaders as well as Russian Foreign Minister Sergei Lavrov and Turkish Prime Minister Ahmet Davutoglu.
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Hundreds of thousands of people have gathered on the Place de la Republique.
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Palestinian president Mahmoud Abbas was among the leaders to have been welcomed to the Elysee Palace by French President Francois Hollande.
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Meanwhile, in east London street artists have put up this tribute to those murdered at Charlie Hebdo.
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Solidarity demonstrations are taking place across Europe, including this one in Madrid, where marchers are holding placards reading, "We are all Charlie".
Get involved
Email talkingpoint@bbc.co.uk
Jon Foster emails: I am an English lawyer living in Paris. In standing up for the freedom of speech, let us remember the difference between satire (and that there is no right not to be offended) and hate speech (to which the European Court of Human Rights has held there is no right).
Let us also not forget the two Muslim heroes, Ahmed Merabet, the policeman who died so horribly in defending Charlie Hebdo's right to ridicule his faith; and Lassana Bathily, who acted so bravely to protect the Jewish customers of the kosher supermarket. These men deserve the strongest recognition as living up to to Voltarian values of the Republic.
Get involved
Email talkingpoint@bbc.co.uk
Euan Wall emails: I am a British student studying at the Sorbonne in Paris. Despite this being exams week, and having three exams in the next two days, my fellow students and I are taking to the streets in Paris to try and show that despite the current political atmosphere, France can unite around ideas like freedom of expression and rejection of barbarity.
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Paris prosecutors are linking the shooting of a jogger to Amedy Coulibaly, the gunman who also murdered a policewoman and four hostages at a kosher supermarket.
The jogger was shot and injured in a Paris suburb on Wednesday, the same day as the Charlie Hebdo massacre, and two days before the supermarket hostage-taking.
The prosecutor said ballistics tests on shell cases from the shooting in Fontenay-aux Roses linked them to the automatic weapon at the kosher store.
Coulibaly and his partner lived in Fontenay-aux-Roses.
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The BBC's James Longman tweets this picture of one demonstrator, called Patrice, who says he's "proud to be here".
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The controversial French comic Dieudonne M'bala M'bala, whose anti-Semitic remarks have in the past sparked a row over the acceptable limits of free speech, tweets: "Attending the march alongside the defenders of freedom of expression. Thoughts for all those who have never been afraid to die laughing."
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More than a million people are expected to attend this afternoon's march. Check out some of the latest pictures from Paris in our picture gallery.
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There have been a number of tales of heroism during the attacks.
They include that of Lassana Bathil, a shop assistant at the Kosher supermarket that was attacked, who led some customers to the store's freezer to hide them from the gunmen.
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BBC journalist Imelda Flattery tweets from Paris: "Rail tickets to Paris from Brussels, Amsterdam and Cologne reduced for the day to 29 euros for the Paris March."
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UK Chief Rabbi Ephraim Mirvis arrives for the Paris march and tells the BBC he's been "saddened and anxious" but that Sunday is about "solidarity with France".
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Earlier on Sunday there was an arson attack at the offices of a German newspaper that reprinted the Charlie Hebdo cartoons of the Prophet Muhammad.
No-one was hurt in the assault on the Hamburger Morgenpost. Two men have been arrested.
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Belgium's interior minister Jan Jambon is calling for a EU list of "foreign fighters" to be set up. In a tweet (in French), he says "co-operation between intelligence services is vital".
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A jarring note is sounded by two prominent Russian politicians, who criticise Ukrainian President Petro Poroshenko for attending today's march in Paris.
The chairman of the Russian parliament's committee for International Affairs, Alexey Pushkov, tweets sarcastically that Poroshenko is attending a march against terrorism, but has failed to take tough action against those responsible for an "act of terrorism" in the southern Ukrainian city of Odessa.
Nationalist politician Eduard Limonov writes on the blogging platform LiveJournal that if Poroshenko, "who ordered the shelling of the peaceful city of Donbass", can take part in the Paris march, then the event is "worthless".
Get involved
Email talkingpoint@bbc.co.uk
Valerie Moreau emails: Hello, I'm French, I'm Parisian and I'm Charlie. I'd like to thank all the people all over the world for being beside us in these terrible days. As murderers try to put us in the dark, all of you and all of us are the lights that won't extinguish. It's really comforting to feel all of you beside us. Thank you, thank you, thank you.
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People gathered in the main square of the village of Dammartin-en-Goele, the village north of Paris where the Charlie Hebdo gunmen , Said and Cherif Kouachi, were both shot dead by police.
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Check out the BBC Arabic's bird's-eye view from a balcony overlooking Boulevard Voltaire, which people will pass through to reach the starting point of the march at Place de la Republique.
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Spain's interior minister says he will call for border controls to be re-established between many EU countries in order to stop jihadists returning from the Middle East.
Interior Minister Jorge Fernandez Diaz told the newspaper El Pais (in Spanish) that it may be necessary to modify the Schengen treaty, which abolished border checks between 26 European countries.
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About 2,000 police officers have been deployed to protect those at the rally. The security presence has been bolstered by 1,350 soldiers - including elite marksmen on rooftops.
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People bearing French flags and tributes to those killed are among tens of thousands of demonstrators gathering in the Place de la Republique, two hours before the march is scheduled to begin.
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Police in France are still hunting for accomplices of those behind this week's terror attacks.
Among those being hunted is Hayat Boumeddiene, the partner of the gunman who attacked a kosher supermarket on Friday.
Check out this report for more details about her.
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The attacks in France have led to soul-searching in other countries. In Britain, the former head of the British Royal Navy, Lord West, warned against a knee-jerk reaction.
"It's a serious threat, but I would say it's the ideal time to be British and have a stiff upper lip and just step back and be calm…" the Labour peer told the BBC.
"This was a horrible incident by murdering, murderous people [but] there is a threat that could happen [here]. We mustn't kid ourselves. They only need to be lucky once, as was famously said once, whereas we have got to be lucky all the time."
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Across the world, people have been paying tribute to the 17 victims of this week's terror attacks. Here are more details on some of those killed.
Sara Firth, Correspondent & Photojournalist, Huffington Post
@Sara__Firth
tweets: The message from many turning out to attend the #Paris #UnityMarch today. #NotAfraid pic.twitter.com/dXsr77WUKF
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French President Francois Hollande will visit the main synagogue in Paris, the Grande Synagogue, after the rally, BFMTV reports, quoting a source in the Elysee Palace. The French paper Le Point carries a similar report, and adds that a ceremony will be held at the synagogue in commemoration of all the victims.
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In a show of solidarity, some of London's most well-known landmarks, including Tower Bridge, Trafalgar Square and the National Gallery, are to be lit in the colours of the French national flag later, in tribute to those who died.
The city's mayor, Boris Johnson, says Londoners have been "appalled" at the attacks, and it was important to "demonstrate our solidarity with the people of Paris".
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Interior ministers from across the world have been holding talks in Paris ahead of this afternoon's march.
French Interior Minister Bernard Cazeneuve says that while it is an informal group, it will lead to concrete action within the European Union. The president of Latvia will host another gathering in coming days.
"The whole of France is in mourning; it is the values of Europe - democracy - that these terrorists wanted to attack," he said.
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Meanwhile, that crowd in the Place de la Republique is swelling. They are chanting "Liberte! Liberte! Charlie! Charlie!" and singing the Marseillaise.
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British Prime Minister David Cameron has tweeted: I'm on my way to Paris to march with the French people. The #CharlieHebdo murders will not crush our spirit or our values.
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Across the border in Germany, police in the northern city of Hamburg have arrested two men on suspicion of carrying out an arson attack against a newspaper which republished cartoons from Charlie Hebdo.
Rocks and a burning object were thrown through the window of the offices of the Hamburger Morgenpost early on Sunday.
Two rooms on the lower floors were damaged but the fire was quickly extinguished and no-one was hurt.
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Crowds are already gathering in Paris' Place de la Republique ahead of this afternoon's march.
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French President Francois Hollande has reassured the country's Jewish community that they will be protected in the wake of Coulibaly's attack on the kosher supermarket which left four people dead.
He made the assurance at a meeting with Jewish leaders at the Elysee Palace. One of those who attended said new security measures to protect synagogues and Jewish institutions would be put in place from today.
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Text accompanying the video says Coulibaly was behind the deaths of a policewoman and "five Jews", also claiming he had planted a bomb on a car in Paris.
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The seven-minute, slickly edited video shows Coulibaly variously doing press-ups, dressed in robes, and displaying an array of automatic weapons and handguns.
Asked whether he has links with the Charlie Hebdo killers, Cherif and Said Kouachi, he says: "The brothers of our team were split into two groups… I went out a bit against the police.
"If we did things a bit together and a bit separately, it was to have more impact."
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A video has emerged in which Coulibaly, who also reportedly shot dead a policewoman on Thursday, claims to be acting on behalf of Islamic State (IS). In the video, he pledges his allegiance to Caliph Ibrahim al-Baghdadi, the head of IS, and says he was co-ordinating his attacks with the two brothers who attacked the Charlie Hebdo offices on Wednesday.
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Hayat Boumeddiene, the partner of Amedy Coulibaly - who attacked a kosher supermarket in eastern Paris on Friday, killing four hostages and taking hostages before being killed by police - is still wanted by police. She is thought to have fled France last week.
Officials believe she may have entered Turkey en route to Syria.
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Meanwhile, French police are still seeking accomplices of the gunmen who attacked satirical magazine Charlie Hebdo and a kosher supermarket.
Eleven people were killed at the magazine offices in Paris on Wednesday, with a policeman shot dead nearby. Four hostages died at the supermarket on Friday.
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About 2,000 police officers and 1,350 soldiers are being deployed in Paris to protect more than a million marchers.
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We'll be bringing you all the latest news from the French capital, where huge crowds and some 40 world leaders are expected later for a massive unity rally through the city.
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Hello and welcome to our coverage of events in Paris, still reeling from three days of terror attacks this week which killed 17 people.