MercoPress. South Atlantic News Agency

PM Cameron promises to hunt down IS murderers of British hostage

“We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes.”

Britain's Prime Minister David Cameron chaired a meeting of the government's emergency response committee on Sunday under growing pressure to sanction air strikes after an Islamic State video showed the beheading of a British hostage.

Footage of the murder of David Haines by IS militants fighting in Iraq and Syria means Cameron, who is also trying to persuade Scotland to reject independence in a referendum on Thursday, is under pressure to get much tougher with IS.

He has said he isn't ruling out any options to degrade IS, with the exception of putting boots on the ground, but is facing increasingly loud calls from some of his own Conservative lawmakers and from former military chiefs to join the United States in launching air strikes.

Cameron's last attempt to get the British parliament to back such air strikes, against Syria last year, ended in failure when lawmakers voted against such action.

With Scotland his domestic priority, he is aware that many Scots have traditionally been more skeptical of British military action overseas and that proposing air strikes now could risk alienating them before Thursday's independence vote.

Cameron, who returned to London ahead of schedule on Saturday night to chair the emergency meeting, has called the murder of Haines, a 44 year-old Scottish aid worker, an act of pure evil and vowed to bring his killers to justice.

“This is a despicable and appalling murder of an innocent aid worker,” he said in a statement on Saturday.

“We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes.”

Britain's Foreign Office said the video showed “all signs” of being genuine.

Haines's executioner appears to be the same man who featured in videos with Foley and Sotloff. The man, nicknamed “Jihadi John” by Western media, seems to have a British accent. At the end of the same video, another hostage is shown and threatened.