Steven Sotloff's mother in plea to IS: Free my son

The mother of Steven Sotloff, a US journalist being held by Islamic State (IS) militants, has made an emotional video appeal for his release.

Shirley Sotloff addressed her plea directly to Abu Bakr al-Baghdadi, the leader of the militant group.

Mr Sotloff, who vanished last year in Syria, appeared in a video showing the killing of US journalist James Foley.

The militant on the video said his life depended on the next move of US President Barack Obama.

The US has recently carried out dozens of air strikes against IS targets in Iraq.

In her video message, Mrs Sotloff described her son as a journalist who had travelled to the Middle East to cover the "suffering of Muslims under the hands of tyrants".

"Steven has no control over the actions of the US government. He's an innocent journalist. I've always learned that you, the caliph, can grant amnesty. I ask you to please release my child," said Mrs Sotloff.

"I ask you to use your authority to spare his life and to follow the example set by the Prophet Muhammad."

Mr Sotloff's case was not widely reported after his mother was told by IS militants he would be killed if she publicised it.

But last week, Mr Sotloff appeared at the end of an IS video showing the beheading of James Foley.

The masked militant who beheaded Mr Foley held Mr Sotloff by the collar and said: "The life of this American citizen, Obama, depends on your next decision."

Analysis: Christopher Voss, ex-FBI hostage negotiator, CEO of Black Swan Group

Shirley Sotloff was respectful of the kidnappers, and that was wise of her. Demonstrating respect is one of the best things to do in these situations, and it's also one of the hardest things.

The chances of success are slim, and it takes a lot of courage to try something that most likely will fail. To be able to pull yourself together and choose this kind of approach is an indication you're an extremely strong human being.

Still it's a wise choice. I believe she would never be able to forgive herself if she hadn't gone ahead and tried.

Earlier on Wednesday, another US journalist who was recently freed by militants in Syria, thanked everyone who had helped with his release.

Peter Theo Curtis, 45, was released on Sunday after being held captive for almost two years by al-Nusra militants.

"I had no idea so much effort was being expended on my behalf," Mr Curtis said.