British Prime Minister David Cameron has confirmed the “brutal murder” of aid worker Alan Henning by the Islamic State group and has vowed to bring his killers to justice.

“The brutal murder of Alan Henning by ISIL (another term for IS jihadists) shows just how barbaric and repulsive these terrorists are,” Cameron said in a statement released by his Downing Street office on Friday.

“We will do all we can to hunt down these murderers and bring them to justice.”

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A video that emerged on Friday showed Henning on his knees against a desert backdrop and wearing an orange prison-style outfit, as a masked militant stood over him wielding a combat knife. The video then showed his beheading.

Henning, a 47-year-old from Manchester in northwest England who volunteered to drive in an aid convoy to Syria for Muslim charity Aid4Syria, was kidnapped 10 months ago.

Cameron said the fact Henning was captured and killed while trying to help others “demonstrates that there are no limits to the depravity of these ISIL terrorists”.

He added that his “thoughts and prayers” were with Henning’s wife Barbara, their children and friends.

And US President Barack Obama also condemned the killing, vowing to bring those responsible to justice.

“Standing together with a broad coalition of allies and partners, we will continue taking decisive action to degrade and ultimately destroy ISIL,” he said in a statement, referring to the Islamic State jihadist group that killed the aid worker.

In the video, a masked IS fighter beheads Henning and threatens a US captive, aid worker Peter Kassig.

The footage, almost identical to three previous execution films released by the group, caused revulsion around the world.

“Mr Henning worked to help improve the lives of the Syrian people and his death is a great loss for them, for his family and the people of the United Kingdom,” Obama said in the statement.

“Standing together with our UK friends and allies, we will work to bring the perpetrators of Alan’s murder – as well as the murders of Jim Foley, Steven Sotloff and David Haines – to justice.”

American reporters Foley and Sotloff, and Haines, a British aid worker, were all previously executed on camera.