Wednesday is the 70th anniversary of the Great Terror Enlarge Image

He gave a speech at the Butovo site where thousands were killed in 1937 at the height of Joseph Stalin's purges.

Mr Putin used the occasion to call for political argument to be "creative rather than destructive".

Campaigning is about to start for Russia's parliamentary elections. Mr Putin's supporters seem certain to win.

He is heading the United Russia party's list of candidates. He is expected to step down as president next year.

Victims 'ignored'

The BBC's James Rodgers in Moscow says Mr Putin's decision to go to Butovo now seems highly significant, since an August ceremony to erect a memorial to victims was not attended by any senior Kremlin officials.

He used to head the Federal Security Service, the modern-day successor to Stalin's dreaded secret police, the NKVD.

Addressing crowds, Mr Putin called for calm ahead of the elections.

"Of course political battles and political arguments and the fight of opinions is necessary, but we need for that process not to be destructive, for it to be constructive," he said.

However, human rights activists in central Moscow said the Kremlin was not doing enough to help victims of repression.

Sergei Volkov, head of the Association of Victims of Political Repression, said they received little or no benefits from the state.

"It's the fault of the man who has stepped with one foot into democracy and still stands with another in KGB - our president, Vladimir Putin," he said, quoted by the Associated Press news agency.

At least 20,000 people were shot at Butovo.

Seventy years ago, Stalin launched his campaign against anyone he saw as a threat to his regime. Those included political opponents, and members of the clergy.

Some were simply unlucky enough to have enemies who denounced them to the NKVD for treachery, real or imagined.

Today, many Russians prefer to remember Stalin as a victorious wartime leader, rather than the architect of mass political killings, our correspondent says.