Looking for His glorious appearing! Titus 2:13

The unconfirmed reports, which contain pictures and video footage of hundreds of soldiers being led into the desert dressed only in their underwear, were circulated on social media by IS supporters early this morning.

Unlike in previous Islamic State propaganda exercises, no pictures have yet been circulated of dead or mutilated bodies. This comes after Twitter late last week cancelled the accounts of any Twitter user who circulated images of the decapitated photojournalist James Foley.

But the accuracy of the pictures and video footage is being disputed, with some Syrian sources saying the men being marched into the desert were actually Sheytat tribesmen being executed earlier this month.

Neither side can be considered trustworthy, with a new UN report delivered to the General Assembly stating both President Assad’s government forces and the various rebel groups fighting them are guilty of “crimes against humanity”. The report details massacres, systematic murder, torture, rape and “enforced disappearance”.

The unverified claim of mass-murder came at the same time IS fighters released pictures purporting to show an Iraqi attack helicopter being hit by an anti-aircraft missile in the vicinity of Tikrit. Iraqi government officials are yet to comment on the claim.

The footage is just the latest in a stream of images showing mass killings after the capture of a strategic air base in Syria — including masked militants shooting kneeling men.

The UN commission in Geneva yesterday accused the Islamic State group of committing crimes against humanity as the photos emerged of the extremists’ bloody takeover of the Syrian military air base.

In one photo posted online earlier this week, masked gunmen were seen shooting seven men kneeling on the ground, some dressed in what appeared to be Syrian military uniforms, after the seizure of the Tabqa air base in the north-eastern Syrian province of Raqqa earlier this week.

The 36 photos and video images corresponded to reporting by The Associated Press of the Islamic State militants’ seizure Sunday of the air base, which had been the last government-held outpost in Raqqa, a province now dominated by the jihadi group. Militants also captured the bases’ weaponry, including artillery and mounted machineguns.

The images underscored how the group uses violence, and images of violence to terrorise its opponents, as it sweeps further into Syria and Iraq, where it has imposed an Islamic state, or caliphate, governed by its harsh interpretation of Islamic law.

Some photos showed captured Syrian soldiers, some with bloodied and swollen faces. In one, a masked Islamic State fighter stood behind a group of soldiers brandishing a knife of the type the militants have used is the past to behead victims, including Foley. In another, a militant grinned as he pressed a double-edged sword against the neck of a captured soldier inside a jeep.

One photograph showed a headless corpse, while another showed 10 slain men, sprawled in a pool of blood on a dirt road. It wasn’t clear if they were killed after fighting or during clashes. Video uploaded to social media networks of the battle showed the charred bodies of Syrian soldiers as Islamic music played in the background.