militants have released a video depicting the murder of British aid convoy volunteer Alan Henning, three weeks after warning that he would be the next to die.
Henning is the fourth western hostage to have been killed by the group, following the filmed beheadings of US journalists James Foley and Steven Sotloff, and Scottish aid worker David Haines.
A further hostage, Hervé Gourdel, from Nice in France, was murdered by Jund al-Khalifa, a group with links to Isis, on 24 September.
The killing comes after the UK launched air strikes against Islamic State (Isis), joining the US and its Arab allies – Jordan, Saudi Arabia and the UAE – which had been targeting the group for several days.
Shortly before the Ministry of Defence announced that the RAF had attacked two Isis targets, the Foreign Office arranged for Henning’s wife Barbara to make a televised appeal for his release.
Intelligence agencies on both sides of the Atlantic are studying the video, which was released on the eve of the Islamic festival of Eid al-Adha.
On Friday night, the Foreign Office said: “We are aware of the video and are working urgently to verify the contents. If true, this is a further disgusting murder. We are offering the family every support possible; they ask to be left alone at this time.”
The prime minister, David Cameron said: “The brutal murder of Alan Henning by Isil [Isis] shows just how barbaric and repulsive these terrorists are. My thoughts and prayers tonight are with Alan’s wife Barbara, their children and all those who loved him.
“Alan had gone to to help get aid to people of all faiths in their hour of need. The fact that he was taken hostage when trying to help others and [has] now [been] murdered demonstrates that there are no limits to the depravity of these Isil terrorists. We will do all we can to hunt down these murderers and bring them to justice.”
The foreign secretary, Philip Hammond, tweeted late on Friday night: “Saddened and appalled. Terrorist murder of humanitarian aid volunteer Alan Henning shows what #ISIL stand for.”
In the video, entitled Another Message to America and Its Allies, a masked man stands behind Henning, who kneels in front of him. Henning says: “I am Alan Henning. Because of our parliament’s decision to attack the Islamic State, I – as a member of the British public – will now pay the price for that decision.”
A voice then says: “The blood of David Haines was on your hands, Cameron. Alan Henning will also be slaughtered, but his blood is on the hands of the British parliament.”
The video ends with a threat to a fifth hostage, a young American man, named by his captors as Peter Edward Kassig. The voice says: “Obama, you have started your aerial bombardment in Sham [Syria and Iraq] which keeps on striking our people. So it’s only right we continue to strike the necks of your people.”
On Friday night, Barack Obama said the US, along with its allies, would continue to take action to destroy Isis. He said: “The United States strongly condemns the brutal murder of United Kingdom citizen Alan Henning by the terrorist group Isil.
“Mr Henning worked to help improve the lives of the Syrian people and his death is a great loss for them, for his family and the people of the United Kingdom.
“Standing together with our UK friends and allies, we will work to bring the perpetrators of Alan’s murder – as well as the murders of Jim Foley, Steven Sotloff and David Haines – to justice. Standing together with a broad coalition of allies and partners, we will continue taking decisive action to degrade and ultimately destroy Isil.”
The video follows the same structure as the three previous Isis beheading videos. It begins with a news clip – this one taken from the Russian channel RT – featuring a presenter describing the seven-hour debate in the British parliament that culminated in the approval of UK strikes on Isis targets in .
It is followed by footage showing Henning – in an orange tunic, kneeling beside his apparent killer – delivering a speech presumably written by his captors. The killer wears a black face mask and carries a knife in his left hand. As with earlier videos, it shows the start of Henning’s apparent murder before moving away. Henning’s body and severed head are then shown on the ground.
The video appears to have been filmed in an area similar in topography to the landscape shown in the Haines, Sotloff and Foley videos. It is not clear when the video was made, although Henning refers to “our parliament’s decision to attack Islamic State”, the vote for which took place on 26 September. He does not refer to the first RAF strikes, which were conducted on 30 September.
The young American appears at the end of the video. A man with the same name as Kassig, and resembling him, appeared in a CNN profile from 2012. That profile describes Kassig as an Indiana native and a former US soldier who fought in the Iraq war. Kassig trained as an emergency medical technician in 2010, and moved to Lebanon in 2012 to provide aid to refugees of the Syrian crisis, .
Lisa Monaco, the US president’s top counter-terrorism adviser, told a White House briefing that the administration was working to authenticate the video. “This is yet another demonstration of the brutality of Isil,” she said, using the administration’s preferred acronym for the militants.
The UN Security Council called the killing a “heinous and cowardly murder”.
In a statement late on Friday it said such “acts of barbarism” did not intimidate council members, but rather stiffened their resolve.
The current president of the council, Argentina’s ambassador, Maria Cristina Perceval, read the statement to reporters. She did not say whether the UN had verified the video and did not answer questions.
Before reading the statement, she remarked: “What a world.”
Henning, 47, a taxi driver from Eccles, Greater Manchester, had been held captive in Syria for nine months, and is thought to have been held by Isis with up to 20 other western hostages for much of that time. Described by friends as “a big man with a big heart”, Henning fell into the group’s hands after joining a group of Muslim friends on an aid convoy to Syria last Christmas.
It was the second time in nine months that Henning had joined an aid convoy to Syria, after helping to raise funds to purchase the ambulances and medical equipment being taken into the country. Other volunteers on the convoy have since described how he was separated from them after armed men surrounded a warehouse a short drive from the Turkish border, where they were delivering ambulances and medical equipment.
The gunmen claimed that they were suspicious about Henning because he was not a Muslim, and because he had a chip in his UK passport. He was taken away despite the other volunteers demonstrating that all UK passports carried such a chip.
Henning was shown and named in a previous video by Isis, which depicted the murder of Haines, 44, a father of two from Perth in central Scotland.
At the end of the video, entitled A Message to the Allies of America, Haines’s killer was seen holding Henning by the collar of the orange jumpsuit in which he was dressed, and saying in a distinctive London accent: “If you, Cameron, persist in fighting the Islamic State, then you, like your master Obama, will have the blood of your people on your hands.”
Since the Haines video appeared online, several leading Muslims had called for Henning to be released. One of them, Sheikh Haitham al-Haddad, said Henning’s murder would be “impermissible” under Islamic law.
Henning’s wife, Barbara, had asked Isis to “see it in their hearts” to release her husband, whom she described as a “peaceful, selfless man”. She added: “Surely those who wish to be seen as a state will act in a statesman-like way by showing mercy and providing clemency.”
One of the organisers of the convoy, Kasim Jameel, a taxi driver from Bolton in Greater Manchester, described him as “a man who is full of compassion ... just a normal bloke, an everyday taxi driver who wanted to do good”.
The release of the video showing Haines’ murder and the threat to Henning’s life was followed by three more videos in which John Cantlie, a British photographer who has been held hostage by Isis for 22 months, delivered propaganda messages on behalf of the group.
and spoke of his family’s “despair and helplessness” after seeing his son appear on a video released on the internet. Delivering his appeal in a video, he said: “To those holding John: please know that he is a good man. He sought only to help the Syrian people, and I ask you from all that is sacred to help us to allow him to return safely to those he loves and those who love him.”
Isis has also released an hour-long film about its advance across Syria and Iraq. In its final scene, a masked man with an American-sounding accent delivers a speech standing by Syrian soldiers who have been forced to dig their own shallow graves. It closes with the murders of the men.