UPDATE 1400 GMT: The parents of Peter Abdul-Rahman Kassig have issued a statement asking the news media to “avoid playing into the hostage takers’ hands and refrain from publishing or broadcasting photographs or video” of the execution: “We prefer our son is written about and remembered for his important work and the love he shared with friends and family, not in the manner the hostage takers would use to manipulate Americans and further their cause.”

The Islamic State claimed on Sunday that it beheaded another American hostage, aid worker Peter Abdul-Rahman Kassig.

The jihadists uploaded a video in which a masked executioner with a British accent announced the killing and stood over Kassig’s severed head.

The Islamic State also executed 18 captured Syrian troops.

The executioner appeared to be the same jihadist who beheaded US journalists James Foley and Steven Sotloff and British aid workers David Haines and Alan Hemming.

He said, apparently after Kassig refused to make a statement:

This is Peter Edwards Kassig, a US citizen of your country. Peter, who fought against the Muslims in Iraq whilst serving as a soldier in the American army, doesn’t have much to say. His previous cellmates have already spoken on his behalf.

But we say to you, Obama … you claim to have withdrawn from Iraq four years ago. We said to you then that you were liars, that you had not withdrawn. And that if you had withdrawn you would return even after some time – you would return….

Your forces will return greater in number than they were before. We also remind you of the haunting words of our Sheikh Abu Musab al-Zarqawi [the founder of Al Qaeda in Iraq] told you. The spark has been lit here in Iraq and its heat will continue to intensify by Allah’s permission until it burns the crusader army.

The Islamic State has executed hundreds of men in Syria and Iraq as it has battled local forces and extended its control over areas of both countries since the spring.

Kassig, a former US Army Ranger who served in the 2003 Iraq War, later trained as an emergency medical technician. He travelled to Lebanon in May 2012 to work in border hospitals treating Palestinian refugees and those fleeing the Syrian conflict.

Later in the year, he founded Special Emergency Response and Assistance, moving its base of operations to southern Turkey, near the border with Syria. SERA sourced and delivered supplies to camps on both sides of the Syrian border, and helped to treat civilian casualties and train medics inside Syria.

In 2013, Kassig began working in Deir Ez Zor Province in eastern Syria. He was abducted in October at an Islamic State checkpoint.

In the video, about 20 Islamic State fighters stood over the captured Syrian soldiers as the masked executioner again addressed Washington:

To Obama, the dog of Rome, today we are slaughtering the soldiers of Bashar and tomorrow we’ll be slaughtering your soldiers. With Allah’s permission we will break this final and last crusade and the Islamic State will soon like your puppet [British Prime Minister] David Cameron said will begin to slaughter your people on your streets.

The executioner said the beheadings took place in Dabiq, north of Aleppo and about 25 km from the Turkish border.