AFP, 14 Sep 2014 – The beheading of a British hostage by Islamic State militants was an “act of pure evil,” Prime Minister David Cameron said Sunday, vowing Britain will do all in its power to bring the killers to justice.
 “This is a despicable and appalling murder of an innocent aid worker. It is an act of pure evil,” he said in a statement released by his Downing Street office.
 “We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes.”
The video appeared less than a day after the aid worker’s family on Saturday appealed to his captors to contact them.
Prime Minster Cameron tweeted that his “heart goes out to his family who have shown extraordinary courage and fortitude.”
Britain’s Foreign Office said they were “working as quickly as we can to try and verify” the video.
Two US journalists have been murdered in similar circumstances in recent weeks.
Scottish-born Haines, 44, was taken hostage in Syria in March 2013 and was threatened in a video released this month depicting the beheading by an IS militant of the US journalist Steven Sotloff.
Haines had been working for the Agency for Technical Cooperation and Development (ACTED), an international relief charity, and was previously involved in humanitarian work in the Balkans, parts of Africa and elsewhere in the Middle East.
Sotloff and fellow US journalist James Foley had also been kidnapped in Syria. IS released a video claiming Foley’s execution on August 19, and Sotloff’s two weeks later on September 2.
In a statement issued by the Foreign Office in London earlier Saturday, Haines’ family had appealed to his captors to contact them, saying the extremists had not responded to any of their attempts at communication.
“We are the family of David Haines. We have sent messages to you to which we have not received a reply. We are asking those holding David to make contact with us,” the family said.