A video, which appears to shows Syrian rebels summarily executing a group of unarmed men sparked international outrage today, increasing concerns about the make-up of the plethora of armed groups fighting in an increasingly dirty war.
The UN joined human rights groups in accusing the rebels of a possible war crime in the incident apparently filmed after rebels seized a checkpoint near the strategically crucial town of Saraqeb in Idlib province, which was reported to be in Free Syrian Army (FSA) control today.
The video will compound worries about elements within the rebel ranks just days before a key meeting in Doha which aims to forge a new opposition body including more representation from internal groups.
The footage shows a chaotic scene as armed men corral at least 10 captives - thought to be Assad security forces who were manning the checkpoint - into a group on the floor, encircling them and shouting insults. "Animal!" one cries out, "Assad dogs!" shouts another as several men are kicked the back of the head while they lie face down on the floor. Chants of "God is Great!" drown out the pleading cries of the captives, before the shouting is broken by the sound of gunfire, and a rain of bullets kicks up dust from the ground above a pile of twitching corpses.
"The allegations are that these were soldiers who were no longer combatants and therefore, at this point, it looks very like a war crime. Another one," said Rupert Colville a spokesman for the UN High Commissioner for Human Rights. "The people committing these crimes should be under no illusion that they will escape accountability."
Amnesty International, the first to highlight the footage, described it as "shocking" saying it "demonstrates an utter disregard for international humanitarian law." Both Amnesty and the UN said they were investigating the video and trying to determine the identity of the gunmen.
The video is titled "prisoners and dead from the regime military at the Hmeisho checkpoint" and dated on Thursday. The checkpoint is just outside Saraqeb, and one of three in the area attacked that day by rebels, who killed a total of 28 Assad soldiers, according to the Syrian Observatory for Human Rights.
The monitoring group said Saraqeb and an area extending 25 km around it had fallen into rebel hands today after Assad troops withdrew, a significant blow to the regime as it attempts to cling onto the northern city of Aleppo where for the past three months the two sides have been locked in the conflict's most high-stakes battle to date.
Highways from Damascus to the south and Latakia, a regime stronghold to the southwest, converge in the town of Saraqeb so the government's ability to resupply its war-weary troops in the north is now severely compromised. The regime had already been impeded when the rebels seized the town of Maarat al Numan, further down the main Damascus highway, a month earlier, but today's gain cuts of both major supply routes from the south.
Both sides have been accused of committing massacres and summary executions of prisoners in the past, but as the bitter 20-month conflict drags on tactics appear to be becoming ever more brutal. Previously the FSA leadership has condemned such acts but can wield little control over the disparate groups on the ground and an influx of foreign Islamic jihadists has further complicated their efforts.
The video will cast a shadow over an opposition meeting in Doha next week, where the US is pushing for a significant shake up of the structure of the Syrian opposition. The Obama administration has called for a more inclusive body to represent the rebellion, voicing concerns that if the opposition does not unite the revolution runs the risk of being hijacked by extremists.
The new council, hoped to function as a transitional government, is expected to be announced in the second half of next week. It will supersede the controversial Syrian National Council (SNC), which includes figures who have spent years in exile and is criticised for being out of touch.
Riad Hijab, Syria's defected prime minister is among those mooted for inclusion as is Riad Seif, a veteran opposition figure who played a key role in formulating the plan. However, members of the SNC have voiced opposition to the initiative while Syria's ally Russia today rounded on the US for its interference, saying the plan contravenes an earlier agreement in Geneva that a transitional government should be agreed by both sides.
*Warning: Graphic scenes of a disturbing nature*