Latest ISIS beheading 'an act of pure evil'

British PM David Cameron has condemned the beheading of a UK aid worker by Islamic terror group ISIS.

FILE. British PM David Cameron has condemned the beheading of a UK aid worker by Islamic terror group ISIS. Picture: Leon Neal/AFP

JOHANNESBURG - British Prime Minister David Cameron is expected to chair a meeting of the government's emergency response committee this morning, after aid worker David Haines was beheaded by the terror group the Islamic State.

British aid worker David Haines. Picture: Facebook.com

A video has been released showing the beheading of Haines, who was abducted in Syria last year.

Cameron has condemned his slaying as 'an act of pure evil'.

Haines is the third Westerner beheaded in recent weeks by the Islamic State group, which has seized vast areas in Syria and Iraq.

The video emerged a day after Haines' family issued a public plea late on Friday, urging his captors to contact them.

The executioner in the video slammed Britain for its stance on Syria and Iraq.

"You're even allies of America, which continues to strike the Muslims of Iraq and most recently formed [a coalition] will only accelerate more destruction.

In the video the executioner makes specific reference to the Prime Minister, saying his decisions have fuelled a war.

"Playing the role of the obedient lap dog, Cameron will only drag you and your people into another bloody and unwinnable war."

Two American journalists taken hostage in Syria, James Foley and Steven Sotloff, were beheaded last month.

At the same time United States President Barack Obama has expressed solidarity with ally Britain, after Haines' beheading.

US Secretary of State John Kerry is currently traveling to meet with his country's allies, hoping to forge a broad international coalition against ISIS in Iraq and Syria, which will include Arab nations.