By Dan Wooding
Founder of ASSIST Ministries
SYRIA (ANS) -- British aid worker David Haines has been "executed" by Islamic State (IS) militants, according to a video posted Saturday to a website associated with the group, making him the third Western captive to be killed by the Islamist extremist group in recent weeks.
In the video a masked militant is seen standing behind a man who appears to be David Haines
The gruesome video post showing Haines' apparent beheading called his execution "a message to the allies of America."
CNN reported, "It is produced very similarly to the videos that showed the executions of American journalists James Foley and Steven Sotloff, the last of which included Haines and the threat that he'd be killed next."
The British Prime Minister, David Cameron, on hearing the shocking news, vowed to do "everything in our power to hunt down" the aid worker's killers.
Cameron said the murder of an innocent aid worker was "despicable and appalling," adding, "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.
"We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes," the Prime Minister added.
Mr. Haines's family said that the 44-year-old, who worked for the Paris-based charity, ACTED (Agency for Technical Cooperation and Development) would be "missed terribly."
The latest video also "includes a threat to kill a second British hostage," said the BBC.
The video of Mr. Haines' execution begins with a clip of Mr. Cameron and then features a man who appears to be Mr. Haines dressed in orange overalls, kneeling in front of a masked man holding a knife. He is believed to be the same person who also executed the two American journalists.
The victim says: "My name is David Cawthorne Haines. I would like to declare that I hold you, David Cameron, entirely responsible for my execution."
The BBC reported that "the militant, who appears to have a British accent, is then recorded as saying: "This British man has to the pay the price for your promise, Cameron, to arm the Peshmerga against the Islamic State."
The UK has donated heavy machine guns and ammunition to authorities in Iraq to help fight IS militants, the Ministry of Defence previously said. Kurdish forces, known as the Peshmerga, have been involved in heavy fighting with IS.
Atmeh camp where Mr. Haines was helping refugees when he was kidnapped
Mr. Haines, a father-of-two, was born in Humberside, East Yorkshire and later moved to Perth, Scotland, and whose parents now live in Ayr, was taken hostage in the village of Atmeh, in the Idlib province of Syria, near the Syrian border with Turkey, in March 2013
He had been helping French agency ACTED deliver humanitarian aid, having previously helped local people in Libya and South Sudan. The release of the video came hours after his family had made a direct appeal to IS to contact them.
US President Barack Obama said "our hearts go out to the family of Mr. Haines and to the people of the United Kingdom."
In a statement he said the US would work with the UK and a "broad coalition of nations" to "bring the perpetrators of this outrageous act to justice." Obama added, "The United States stands shoulder to shoulder tonight with our close friend and ally in grief and resolve."
The BBC also said that senior UK imams and British Muslim community leaders have also condemned the killing.
"An attack on a British citizen is an attack on Britain and we raise our voices as a community united to deplore the actions of the terrorists Isis," Dr. Qari Asim, imam of the Makkah Mosque in Leeds said.
Sayed Ali Abbas Razawi, from Majlis-e-Ulama, which represents the majority of Shia Muslims in the UK and Europe, said militants were hiding behind a "false interpretation" of Islam, describing the group as "criminals and villains."
IS - also known as Isis or Isil - has seized large swathes of territory in Iraq and Syria and declared a new caliphate - or Islamic state.
Militants from the extremist group have killed two US hostages in recent weeks, posting video evidence on the internet.
They threatened to kill Mr. Haines during a video posted online showing the killing of US journalist Steven Sotloff earlier this month. The extremist group also killed fellow US journalist, James Foley, last month.
In a statement released a few days after Mr. Haines's name became public, ACTED said it was "deeply shocked " by the images of him being held by his captor.
"David has been working as a humanitarian since 1999, helping victims of conflict in the Balkans, Africa, and the Middle East," it said. "When he was taken hostage in March 2013, David was in Syria as part of ACTED's humanitarian effort in support of tens of thousands of people affected by the crisis."
The statement added, "A man's life should never be threatened on account of his humanitarian commitment."