A video reportedly released Sunday by the Islamic State group shows the execution of five prisoners identified as British spies. Narrated by a masked gunman speaking British-accented English, the 10-minute clip came as an explicit challenge to U.K. Prime Minister David Cameron.

“This is a message to David Cameron,” the man says in the video. “How strange it is that a leader of a small island threatens us with a handful of planes,” he says, mocking British military efforts to hobble the militant group’s advances in Iraq and Syria.

In the video, five men are depicted kneeling in orange jumpsuits before masked gunmen. After being accused of spying for Britain, they each deliver a confession in Arabic. They report hailing from Syria and Libya. At the end of the video, each is shot in the head. 

Screen Shot 2016-01-03 at 12 Prisoners are seen kneeling before their execution in an Islamic State group propaganda video. Photo: YouTube/Screenshot

The main speaker recalls the fighter dubbed Jihadi John, a British Arab who appeared in earlier clips released by the militant group aka either ISIL or ISIS, such as the video that depicted the beheading of American journalist James Foley. U.S. officials reported killing Jihadi John, whose real name was Mohammed Emwazi, in a November drone strike.

A young English-speaking boy also appears in the video, making reference to killing nonbelievers.