ISIL threatened Britain in an Internet video Sunday showing the killing of five "spies" it said worked with the US-led coalition against the terrorist group in Iraq and Syria.

The Takfiri group, ISIL (so-called Islamic State in Iraq and Levant) threatened Britain in an Internet video Sunday showing the killing of five "spies" it said worked with the US-led coalition against the terrorist group in Iraq and Syria.

The SITE Intelligence Group said the video shows five men from Raqa, capital of the self-declared Takfiri so-called "caliphate" straddling Syria and Iraq, confessing to carrying out acts of espionage.

The British foreign office issued a terse statement saying only: "We are aware of the video and are examining the content."

In the footage, an English-speaking ISIL militant mocks British Prime Minister David Cameron for challenging ISIL, and calls him an "imbecile".

The "confessions" of the five do not clearly identify which countries they worked with, but one mentions the US-led coalition against ISIL in Iraq and Syria.

The video said they passed videos or photos of the living conditions in Raqa to people in Turkey, or monitored the movements of ISIL terrorists.

The five are seen wearing orange jumpsuits and kneeling before five masked militants, all in military fatigues and armed with pistols.

"This is a message to David Cameron," says one of the gunmen, speaking in a British accent.

He says those who want to continue fighting "under the banner of Cameron" should ask themselves what would happen to them if they were to fall into ISIL hands.

He also says ISIL will wage “jihad” against Britain, before the five men are killed with a bullet to the head.