Islamic State has released a video appearing to show the beheading of American hostage Peter Kassig.

The IS militant in the footage speaks with a London accent and appears to be the same man responsible for previous hostage killings, known as Jihadi John.

Mr Kassig was captured in Syria in October last year while providing medical training and humanitarian aid to victims of the country's conflict.

Previous beheading videos showed a desert landscape but in this latest release the IS militant - who says he is in Iraq - appears to be in front of a town with fields in the distance.

Mr Kassig's severed head is shown at the feet of a militant wearing black trousers and military-style khaki boots.

David Cameron said earlier today that he wants Jihadi John to face justice, after reports that he was injured in an allied air strike against IS commanders in Iraq.

The masked fanatic, believed to be responsible for the beheading of two British and two American hostages, is reported to have been taken to hospital after narrowly escaping death in the raid.

The Prime Minister declined to comment on the specific operation, but said the message should go out to anyone considering travelling to Syria or Iraq to fight for the militant group that they are ''putting themselves in harm's way''.

Speaking at a press conference at the G20 summit in Australia, Mr Cameron said: ''You should be in no doubt that I want Jihadi John to face justice for the appalling acts that have been carried out in Syria, but I wouldn't make any comment on individual issues and strikes.

''The point is clear that if people travel to Syria or Iraq in order to conduct terror operations against British people, British citizens or people back here in Britain, then they are putting themselves in harm's way and they shouldn't be in any doubt about that.''

Reports suggested that Jihadi John was injured in a US-led air strike last weekend on a summit of IS leaders in the town of Al Qaim, in Anbar province, near Iraq's border with Syria.