LONDON - A video released on the Internet on Friday appears to show British hostage Alan Henning being beheaded by a masked fighter for the Islamic State of Iraq and Syria, the militant monitoring group Site Intelligence reported.
Henning, 47, a former taxi driver from the Manchester area, had been held captive in Syria for nine months after traveling to the crisis-torn region to assist with humanitarian relief work in the nearly 4-year-old civil war.
ISIS fighters have seized broad swaths of Syria and Iraq in recent months and in June proclaimed a "caliphate" in that territory, where they have rampaged against less extremist Muslims and adherents of other faiths. Thousands have been killed by the group, provoking U.S.-led airstrikes aimed at its strongholds.
The 71-second video released Friday, titled "Another Message to America and Its Allies," also shows the militant threatening another hostage, whom Site identified as Peter Edward Kassig, an American aid worker.
"Obama, you have started your aerial bombardment of Shams (Syria), which keeps on striking our people, so it is only right that we strike the necks of your people," the dagger-wielding man warned, according to a translation of the video by the Associated Press in Cairo.
The AP said it couldn't verify the video's authenticity but described it as similar in content and format to three other recordings released by ISIS depicting the executions of American journalists James Foley and Steven Sotloff and Scottish aid worker David Haines.
ISIS also claimed to have orchestrated the execution of a fifth Western captive, French tourist Herve Gourdel, who was kidnapped while trekking in Algeria's mountainous Kabylie region Sept. 21 and was shown being decapitated in a video obtained by the Site group two days later. Gourdel, 55, was killed by an ISIS-affiliated militant group known as Jund Khilafah, or Soldiers of the Caliphate.
Kassig, whose detention by ISIS had not been widely disclosed before Friday, has been identified as an Indiana native and former U.S. Army Ranger who served in Iraq in 2007. A January 2013 Time magazine article on Kassig, 26, said he had formed an aid group after his discharge from the army to help Syrian refugees in Lebanon.
A statement issued by the White House condemned Henning's "brutal murder."
"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," the Obama administration stated. "Standing together with a broad coalition of allies and partners, we will continue taking decisive action to degrade and ultimately destroy ISIL."
The militants claiming responsibility for the killings are also known as the Islamic State in Iraq and the Levant, or ISIL.
The video of Henning released Friday appears to show the same British-accented executioner seen in the recordings of the Foley, Sotloff and Haines slayings.
Henning, a married father of two known to his friends as "Gadget" for his technical savvy, was kidnapped in Ad Dana, Syria, shortly after crossing the border from Turkey on Dec. 27.
British authorities said they were still examining the video and had no immediate comment on the purported execution of Henning.
The threat against Henning prompted British Muslim organizations and key figures within Britain's Muslim community to appeal for his release.
Henning's wife, Barbara, had issued several messages directed at ISIS asking that her husband be freed and highlighting his desire to help the people of Syria.
"When he was taken he was driving an ambulance full of food and water to be handed out to anyone in need," she said.
"His purpose for being there was no more and no less. This was an act of sheer compassion."
The family later received an audio recording of Henning pleading for his life to be spared, after which Barbara Henning issued a second statement by video this week.
Amandla Thomas-Johnson, a spokesman for Cage, a British organization that has campaigned for Henning's release, described Henning as "courageous and brave" and "willing to put others' suffering before the relative luxuries of life in the UK."
"Our thoughts are with the family of Alan Henning, and also his friends," Thomas-Johnson said. "ISIS's actions ... what they've done is inconsistent with Islamic law."
But he criticized the British government for not doing more to secure Henning's release and for its decision to join U.S.-led airstrikes against ISIS.