LONDON

 World leaders have condemned the beheading of a British aid worker by Islamic State militants as the U.K. confirmed David Haines death on Sunday.

 “All the signs are that the video is genuine; we have no reason to believe it is not,” Britain's Foreign office said in a statement.

 In earlier statements, U.S. President Barack Obama condemned the killing while British Prime Minister David Cameron said: "This is a despicable and appalling murder of an innocent aid worker. It is an act of pure evil."

 "My heart goes out to the family of David Haines who have shown extraordinary courage and fortitude throughout this ordeal," he added.

 Leading politicians from France, Germany and the Kurdish Regional Authority also denounced the execution.

 A video - released late Saturday - shows a masked militant beheading the 44-year-old U.K. national in similar circumstances to previous IS footage of the murders of U.S. journalists James Foley and Steven Sotloff.

 Cameron said that the government would do everything in its power "to hunt down these murderers and ensure they face justice, however long it takes.”

 The Foreign Office had been working to verify the video. 

 Haines was working for a French aid agency in Syria when he was kidnapped in March 2013.

 The video - which runs for almost 2 1/2 minutes is titled “A Message to the Allies of America.” As was the case in previous videos featuring Foley and Sotloff it shows the purported victim decrying his government’s actions against IS.

 Haines says: “You [David Cameron] entered voluntarily into a coalition with the United States against the Islamic State just as your predecessor Tony Blair did following a trend amongst our British prime ministers who can't find the courage to say no to the Americans.”

 "Unfortunately it is we - the British public - that in the end will pay the price for our parliament's selfish decisions," he adds.

 The executioner - who appears to be the same man in the previous videos - says in what appears to be a British accent that the UK's alliance with the U.S. will only “accelerate your destruction” and drag the British people into “another bloody and unwinnable war.”

 "This British man has to pay the price for your promise, Cameron, to arm the Peshmerga [Kurdish forces] against the Islamic State."

 Britain has been trying to identify the man, to determine if he is indeed a British citizen.

 As was the case with the previous videos, the latest closes with a threat to kill another hostage - in this case a second British man.

 The Foreign Office released a statement from Haines' brother Mike on Sunday, in which he talked about how his brother helped "whoever needed help, regardless of race, creed or religion." 

 “David was most alive and enthusiastic in his humanitarian roles. His joy and anticipation for the work he went to do in Syria is for myself and family the most important element of this whole sad affair.

 "He was and is loved by all his family and will be missed terribly.”

 In a statement late Saturday, Obama said: “The United States strongly condemns the barbaric murder of UK citizen David Haines by the terrorist group ISIL [IS]. Our hearts go out to the family of Mr. Haines and to the people of the United Kingdom.”

 On Sunday, French President Francois Hollande, German Foreign Minister Frank-Walter Steinmeier and Kurdish Regional Government President Massoud Barzani issued statements condemning the murder.

 “The heinous killing of David Haines is a hateful murder and is another demonstration of why the international community must take action against this terrorist organization,” Hollande’s office said.

 Steinmeier described the killing as "a terrible and barbaric act beyond all limits of humanity and civilization."

 Barzani’s spokesman Umit Sabah said: "We sharply condemn the killing of Haines without respecting any humanitarian, religious or moral values."

 IS  - previously known as Islamic State of Iraq and Levant - is in control of large chunks of land in both Iraq and Syria.

 The U.S. has led efforts to form a regional and international coalition to fight the threat posed by the group, the U.K. donating heavy machine guns and ammunition to Iraqi authorities in the fight.

www.aa.com.tr/en