British Prime Minister David Cameron confirmed the "brutal murder" of aid worker Alan Henning by the Islamic State group on Friday and 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.
"We will do all we can to hunt down these murderers and bring them to justice."
A video which emerged on Friday shows Henning on his knees against a desert backdrop and wearing an orange prison-style outfit, with a masked militant standing over him wielding a combat knife before the video cuts to his beheading.
Read: New video shows Islamic State group beheading British hostage Henning
Henning, a 47-year-old from Manchester in northwest England who volunteered to help drive 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.
The killing was also condemned by the Muslim Council of Britain, the country's biggest Muslim umbrella organisation.
Secretary general Shuja Shafi said it was a "despicable and offensive" act.
"Alan was a friend of Muslims, and he will be mourned by Muslims," he added.
"In this period of Haj and this festival of Eid, Muslims remember the mercy of God and the emphasis God places on human life.
"Alan Henning's murderers have clearly gone against that spirit of Islam."