US President Barack Obama has condemned the "brutal" murder of British captive Alan Henning on Friday, saying the United States would 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 a video released by the group in response to US-led air strikes against it, 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, inspired revulsion around the world and drew a stark warning from Obama and Britain's Prime Minister David Cameron.
"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.
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"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.
