Islamic State (Isis) have released a new video showing the execution of 13 men, accused of being part of a pro-Assad gang.

Entitled "The Execution of a Murtad group linked to the Nusayri regime", the six minute video is slickly produced and uses special effects overlays to give the footage a more sophisticated look.

It opens with each of the 13 prisoners taking it in turns to give their full name and which tribe they come from. A close up shot of each man, focusing on their face, has been edited.

Each victim's testimony is followed by a short glimpse of them kneeling down, waiting in line to be executed.

A masked IS fighter, wearing a leather jacket and civilian clothing, claims he is part of Islamic State's police intelligence network in Raqqa.

He proudly declares that Islamic State have "succeeded in stopping a spy network", before denouncing the group of men as traitors.

He accuses them of accepting thousands of pounds worth of payments from the Assad regime in order to "betray and deceive the Islamic state and all Syrian refugees". The group are accused of killing many civilians through two car bomb attacks.

The leader of the group, who gives his name as Abdul Hamid Hamada, is allowed to speak on behalf of the condemned men. Hamada admits the group were paid to organise two car bomb attacks in Raqqa at the cost of 500,000 Syrian pounds (£1,806) each.

The group were also paid 800,000 Syrian pounds in exchange for information for IS positions at Tabqa air base as well as illegally smuggling people and supplies out of the city.

Each prisoner is then shown with his hands bound behind his back and blindfolded whilst he is dragged onto to the back of a pickup truck.

They are driven into the centre of the city, where they are dragged before a large crowd of residents.

Forced to kneel on the ground in a line, each man's blindfold has been removed. Behind each man, an Islamic State fighter stands, waiting to execute their prisoner.

After a statement is read out about the condemned, each executioner pulls out a pistol and fires a single shot into the head of their prisoner.

Graphic close-up footage of the bodies is shown, whilst IS fighters look on with apparent disinterest at their victims.