David Haines beheading video confirmed genuine; UK PM Cameron vows to hunt down ISIS 'monsters'

London: The United Kingdom on Sunday confirmed that the video of the beheading of one of its citizens David Haines released by the Islamic State or the ISIS terror group was genuine.

In the video released by the terror group, Haines is seen wearing an orange jumpsuit and kneeling in the desert while he reads from a prepared script.

It later shows what appears to be the aid worker's body.

A new 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 British hostage was was captured by militants in Syria in 2013.

The UK Foreign Office said in a statement, "All the signs are that the video is genuine".

Like with previous IS murder videos showing the beheading of US journalists James Foley and Steven Sotloff, it ends with a threat to kill another hostage - a second British national.

IS Beheads Briton David Haines, Threatens to Execute Another Briton, Alan Henning http://t.co/GOgalAc1mA — SITE Intel Group (@siteintelgroup) September 13, 2014

Islamic State releases video showing beheading of British aid worker David Haines — SITE Intel Group (@siteintelgroup) September 13, 2014

INSITE: #IslamicState Beheads Briton David Haines, Threatens to Execute Another Briton, Alan Henning http://t.co/6cpFGOEOOb — SITE Intel Group (@siteintelgroup) September 13, 2014

The emergence of the footage late last night saw Prime Minister David Cameron return to Downing Street after midnight.

He has since chaired a meeting of the government's emergency committee Cobra, and issued a statement afterwards saying that the killing would not change Britain's strategy against the IS. Speaking from Downing Street this morning, the UK PM condemned Haines' killers and said the UK would "hunt down those responsible and bring them to justice, no matter how long it takes", adding, "They are not Muslims, they are monsters", PTI reported.

He described Haines, 44, as a "British hero", and praised the "extraordinary courage" of his family. But while he said that "we have to confront this menace," Cameron added that this will not involve direct British involvement in fighting.

The UK is instead playing a supporting role to the US, providing transport and supplies.

The murder of David Haines is an act of pure evil. My heart goes out to his family who have shown extraordinary courage and fortitude. — David Cameron (@David_Cameron) September 13, 2014

We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes. — David Cameron (@David_Cameron) September 13, 2014

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.

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

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 also condemned the "barbaric murder" of Haines which in recent weeks has killed two American journalists James Foley and Steven Sotloff in the same manner.

"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.

"The United States stands shoulder to shoulder tonight with our close friend and ally in grief and resolve," said the President after the IS posted the video on social media showing the killing of the British citizen.

"We will work with the United Kingdom and a broad coalition of nations from the region and around the world to bring the perpetrators of this outrageous act to justice, and to degrade and destroy this threat to the people of our countries, the region and the world," Obama said.

With Agency inputs