An American woman has pleaded for the life of her journalist son, held hostage in Syria by the Islamic State group, just over a week after self-declared jihadists beheaded a fellow US reporter and threatened more murders.
In a video released on Wednesday, Shirley Sotloff directly addressed the group's leader, Abu Bakr al-Baghdadi, saying her son Steven Sotloff was "an innocent journalist" who had no control over US policy in the Middle East.
The plea came just over a week after the group threatened in a video to kill the 31-year-old unless the US stopped bombing its territory in Iraq. The group murdered James Foley, another American journalist, in the same video.
"You, the caliph, can grant amnesty. I ask you, please, release my child. I ask you to use your authority to spare his life,'' Mrs Sotloff said in the video, which was first broadcast on the Al Arabiya network.
"He is an honorable man and has always tried to help the weak," she said.
Islamic State supporters later on Wednesday shared the video on the internet, but blurred Mrs Sotloff's face because their interpretation of Islam does not allow a woman's face to be shown.
Steven Sotloff has been missing in Syria since August 2013.
Josh Earnest, a spokesman for the US president Barack Obama, said he did not know whether he had seen the appeal, but he said the administration was "deeply engaged" in trying to gain release of all Americans held hostage in the Middle East.
"She obviously feels desperate about the safety and wellbeing of her son, and understandably so, and that is why our thoughts and prayers are with Mr Sotloff's family at this very difficult and trying time,'' Earnest said.
A UN commission in Geneva, meanwhile, accused the Islamic State group of committing crimes against humanity with attacks on civilians, and photos emerged of the fighters'' bloody takeover of a Syrian military airbase.
In one photo posted online, masked gunmen were seen shooting seven men kneeling on the ground, some dressed in what appeared to be Syrian military uniforms, after the seizure of the Tabqa airbase in the northeastern Syrian province of Raqqa earlier this week.
The UN report also said it believed the Syrian regime had used chlorine gas in attacks on rebels, which have been reported previously by Al Jazeera, bloggers and other media organisations.
Syria's President Bashar al-Asad last year agreed to give up his chemical weapons stockpile under a UN-brokered deal.
Chlorine is however a "dual use" substance and was not included on the list of materials to be relinquished.