Peter Kassig beheaded: Isis video purports to show brutal murder of US aid worker

A threat to Kassig's life was made at the end of an earlier video showing the beheading of Alan Henning

Peter Kassig, also known as Abdul-Rahman, was kidnapped last year while carrying out aid work in eastern Syria (AP)

The Isis militant group has released a video purporting to show the killing of the US aid worker Peter Kassig.

The graphic new video, shared on YouTube via Isis-affiliated social media accounts, shows a black-clad militant who appears to be the British national known as "Jihadi John" standing over a severed head.

In a speech addressed to President Barack Obama, the militant claims the head is that of "Peter Edward Kassig, a US citizen of your country, who fought against the Muslims in Iraq while serving as a soldier in the American army".

Mr Kassig served in Iraq in 2007, and in 2013 travelled to Syria as an aid worker. He was captured and taken hostage by militants in October that year. According to his friends, Mr Kassig converted to Islam in captivity and changed his name to Abdul-Rahman.

Isis issued a threat to behead the American at the end of another video showing the murder of the British aid worker Alan Henning more than a month ago, prompting Mr Kassig’s parents, Paula and Ed Kassig, to speak out on the 26-year-old’s behalf. They said they had been doing all they could to try and free their son, and read out extracts from a letter he relayed via a fellow hostage.

Unlike in previous videos showing the killings of the US journalists James Foley and Steven Sotloff and the British aid workers David Haines and Mr Henning, the new footage does not show Mr Kassig alive in front of the camera. Also unlike the previous releases, it includes no threat to the "next" hostage.

A separate part of the almost 16-minute video released today shows militants carrying out the mass beheading of around 16 men claimed to be “officers and pilots” of the Syrian army. Each victim has his own executioner – and the militant known as “Jihadi John” is shown performing one of the murders.

Before the men are killed, “Jihadi John” gives a warning “to Obama” and “your puppet David Cameron” that “today we are slaughtering the soldiers of Bashar [al-Assad] and tomorrow we are slaughtering your soldiers”. “The Islamic State will soon begin slaughtering your people on your streets,” he adds.

Charlie Winter, a researcher for the counter-extremism thinktank Quilliam, said that by showing the act of beheading Isis had “surpassed itself in brutality”.

Mr Winter suggested that Isis was “becoming a bit more desperate and trying to show defiance” after two months where its military offensive appears to have stalled.

It was not possible to independently verify the time or location of the shooting of the video – or any of the claims made by the militants shown.

But Mr Cameron said this morning that he was "horrified by the cold blooded murder" of Mr Kassig, adding that Isis militants "have again shown their depravity".

The US National Security Council said it was working to try and verify the events shown in the new video.

“If confirmed, we are appalled by the brutal murder of an innocent American aid worker and we express our deepest condolences to his family and friends,” a statement read.

The video has been released on the same day as it was reported that “Jihadi John” was wounded in a series of air strikes carried out against Isis leaders last Saturday. While it would be almost impossible to verify if those claims were true, if accurate they suggest that Mr Kassig was killed more than one week ago.

Reacting to those reports, Mr Cameron said at the end of the G20 summit in Brisbane that he would prefer to see the masked British militant “face justice” rather than be killed.