BEIRUT: Syrian opposition fighters seized a compound garrisoned by an Al-Qaeda-linked rebel faction Sunday, in some of the most serious infighting to date within the vast array of rebel groups trying to topple President Bashar Assad, activists said.
The clashes between a loose alliance of opposition brigades and the Islamic State of Iraq and the Levant have spread across northern Syria since they began late last week. The rebel-on-rebel violence marks the strongest pushback yet by moderate and ultra-conservative anti-Assad fighters against radical extremist insurgents linked to Al-Qaeda who have sought to impose their strict interpretation of Islam on opposition-held areas of the country.
The Islamic State of Iraq and the Levant, which has many foreign fighters in its ranks, has clashed repeatedly with more moderate rebel groups since it aggressively pushed into Syria from neighboring Iraq in last spring. The infighting has left scores dead on both sides, and has undermined the overall rebel movement's efforts to oust Assad.
The latest clashes broke out on Friday after residents accused ISIL members of killing a doctor in Syria's northern province of Aleppo. The Britain-based Syrian Observatory for Human Rights said the doctor was found dead after being shot several times.
The newly created Islamic Front, an umbrella group of powerful, mostly ultra-conservative Islamic fighters, issued a statement ordering the ISIL to hand over the doctor's killers so they can stand trial. Clashes later erupted between the groups.
Fighting quickly spread to rebel-held areas of the northeastern province of Idlib and the central province of Hama. On Sunday, the violence widened again, with at least one clash outside of Aleppo pitting ISIL against another Al-Qaeda-linked group, the Nusra Front, said Rami Abdurrahman of the Britain-based Syrian Observatory for Human Rights.
Clashes also erupted in the town of Tabqa in the northern province of Raqqa, where the ISIL is most dominant, said Observatory director Rami Abdurrahman. Other activists reported ISIL was pushed out of the town of Atmeh.
Some of the heaviest fighting Sunday took place in the town of Manbij in Aleppo province, where rebels seized an ISIL compound, activists said. The Observatory said ISIL fighters used car bombs, a tactic usually reserved for attacking government forces, for the first time to defend its territory.
Popular resentment of the ISIL has been brewing in northern Syria for months. The group is seen as particularly brutal, even by the measures of Syria's bloody conflict, for its abductions and killings of anti-Assad activists, journalists and civilians seen as critical of its rule.
But other residents welcome the group for chasing out thugs who terrorized people in opposition-held areas, and for distributing food and aid to the poor.
ISIL is the rebranded version of Al-Qaeda's Iraqi affiliate, which emerged in Iraq's Sunni-dominated Anbar province following the 2003-U.S. led invasion of Iraq.
Last week, the group's fighters seized control of the key Anbar town of Fallujah, scattering Iraqi government forces. It also claimed responsibility for a suicide bombing that targeted a Shiite-dominated Beirut neighborhood.
Some activists hailed the fight against the Islamic State as a second "revolution," but it wasn't clear whether the fighting against the Al-Qaeda-affiliated group could unite the constellation of rebel groups who have failed to forge a unified command over the 2 ½ year conflict against Assad.
The groups battling ISIL come from a series of different rebel coalitions. Some are rivals to each other, and at least one group, the Army of the Holy Fighters, said in a video uploaded to the Internet that they were battling the Islamic State because it did not properly accept Islamic law.
The Western-backed Syrian opposition in exile has welcomed the fighting against the Islamic State, as it sees the group as hijacking its efforts to overthrow Assad.
But the potential loss of rebel-held territory as infighting persists also threatens to weaken Syria's already bruised opposition ahead of an international peace conference scheduled for this month to try to broker a political solution to the civil war.
Syria's pro-government al-Watan newspaper appeared to welcome the infighting, offering this as a headline to an editorial Sunday: "Terrorism eats its sons."