It also underscores the rebels’ inability even more than two years into the conflict to unite around a unified command, as well as the deepening rift between more secular opposition fighters and Islamic extremists in the rebel ranks.

The clashes between rebels affiliated with the Free Syrian Army and fighters from the Islamic State of Iraq and the Levant underscored the growing phenomenon of rebel-on-rebel violence that has sapped strength from the broader anti-Assad movement.

BEIRUT — Western-backed opposition fighters and a faction of Al Qaeda-linked rebels turned their guns on each other Saturday in Syria’s largest city, battling for control of a key checkpoint in the latest eruption of infighting among the forces trying to topple President Bashar Assad’s regime, activists said.


The Britain-based Syrian Observatory for Human Rights said Saturday’s clashes were focused on the strategic checkpoint in Aleppo’s Bustan al-Qasr district that serves as the sole gateway between rebel-held eastern districts and the government-controlled areas in the west.

Earlier this week, Al Qaeda-linked militants seized the checkpoint and closed it for several days, cutting the flow of food supplies to the government-held quarters of the city. That spurred protests by residents suffering from food shortages at the start of the Muslim Holy month of Ramadan.

The Observatory said the fighting rattled the neighborhood throughout the morning, but subsided by the afternoon as the Al Qaeda-linked rebels pulled out of the area. It was not clear which group was in control of the checkpoint, where residents were staging a protest to vent their anger at soaring food prices. The area also witnessed clashes between rebels and government troops.

One of the most troubling outbursts of infighting among opposition fighters took place Friday, when the FSA said one of its commanders, Kamal Hamami, was shot dead by Al Qaeda militants in the Jabal al-Turkoman mountain area in the coastal province of Latakia. Hamami, known as Abu Basir, served in the Supreme Military Council of the Free Syrian Army, a group headed by a secular-minded moderate that has the support of Western powers.


Activists monitoring Syria’s more than 2-year-old conflict have previously reported sporadic infighting among rebel groups over control of the territory they have captured in the north along the border with Turkey. Those clashes were mostly between Kurdish and Arab rebels, and have subsided since a ceasefire agreement was reached earlier this year.

The fighting between moderate and jihadi groups that have for months battled Assad’s regime together have become more frequent in recent weeks. The clashes have largely focused on border crossings with Turkey and vital installations, like bakeries, water wells, gas stations, and checkpoints in the north, according to the Observatory.

Another activist said the fighting is aimed at establishing control over the flow of food and aid to the residents. Each group is also trying to set up governing structures over the territory in the north the opposition has controlled for a year and take a cut of money from goods being smuggled into Syria over the border with Turkey.

The activists did not want to be quoted by name for fear of reprisal from both groups.

Militant Islamic groups, including those with links to Al Qaeda, have been the most effective fighting force on the opposition side in the past year.

They have spearheaded many of the attacks that led to the capture of military bases, towns, and villages and whole neighborhoods in Aleppo.


In late February, Islamic battalions led the assault and conquered the eastern city of Raqqa, making it the first Syrian city to entirely fall under rebel control. Moderate factions are now fighting jihadi groups for a say in running of Raqqa.

In the central province of Homs, video emerged Saturday that appeared to show a government airstrike on the Krak des Chevaliers, one of the world’s best-preserved Crusader castles. Government troops have been pressing an offensive against rebels in the province in recent months, and the town, which goes by the same name as the castle, has been under attack by regime troops for the past four days.

The Observatory said Syrian warplanes carried out at least three airstrikes in the area on Friday, but the activist group could not confirm whether the fortress itself had been hit. It also said government forces have ordered residents to evacuate the town, apparently in preparation for a full-scale attack on the area.

The imposing Krak des Chevaliers held off a siege by the Muslim warrior Saladin nearly 900 years ago, and was lauded centuries later by Lawrence of Arabia. The fortress has already been damaged over the course of the civil war, but if the hit it took Friday is confirmed, it would mark the worst destruction to the building so far.

An amateur video posted to YouTube appeared to show a missile striking one of the castle’s towers, sending a plume of smoke and dust into the sky.