Beirut/London/Washington, September 14
Islamic State extremists released a video showing the beheading of British aid worker David Haines, who was abducted in Syria last year. British Prime Minister David Cameron has condemned his slaying as “an act of pure evil”.

Cameron confirmed Haines' death in a statement late yesterday after the British Foreign Office had said earlier that it was "working urgently to verify the video".

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

David Haines (44) was seized in Syria in 2013. The two-minute-27-second video titled "A Message to the Allies of America" blames Cameron for joining forces with the US, which has said it is at "war" with the jihadists and launched air strikes against them in Iraq.

The latest video showing his killing also includes a threat to kill a second British hostage.

"This is a despicable and appalling murder of an innocent aid worker. It is an act of pure evil," Cameron said, adding that "my heart goes out to the family of David Haines who have shown extraordinary courage and fortitude throughout this ordeal." "We will do everything in our power to hunt down these murderers and ensure they face justice," Cameron said.

Britain on Sunday resisted pressure to join the United States in announcing air strikes against the Islamic State after the militant group beheaded David Haines. Speaking after chairing a meeting of the government's emergency response committee in London, Prime Minister David Cameron said his government was battling IS on numerous fronts but was not, for now, launching air strikes. The video emerged a day after Haines' family issued a public plea late on Friday urging his captors to contact them.

The Foreign Office said it was offering Haines' family "every support possible. They ask to be left alone at this time."

Islamic State militants recently beheaded two American journalists - James Foley and Steven Sotloff - and posted the videos online after the US began launching airstrikes and humanitarian missions in August to aid waning Iraqi and Kurdish security forces in northern Iraq.

The Islamic State group has also put out videos showing the beheading of Kurdish and Lebanese soldiers and the mass shooting of dozens of captured Syrian soldiers. At the end of the video showing the beheading of Sotloff, the Islamic State group threatened to kill Haines next and briefly showed him on camera.

US President Barack Obama has condemned the barbaric murder of a British citizen by Islamic State. "The United States strongly condemns the barbaric murder of UK citizen David Haines by the terrorist group ISIL. Our hearts go out to the family of Haines and to the people of the United Kingdom," Obama said in a statement.

Meanwhile, Australia became the first country to detail troop numbers and aircraft for a US-led coalition fighting Islamic State militants in Iraq. Australia Prime Minister Tony Abbott said on Sunday a 600-strong force comprising some 400 air force personnel and 200 special forces soldiers would be deployed to a US military base in the United Arab Emirates. — Agencies