BEIRUT — Fighting between rebel factions broke out Friday across northern Syria after al-Qaida-linked militants executed a doctor who was attempting to negotiate a reduction in mounting tensions between rival groups.
The execution of Dr. Hussein Suleiman by fighters from the Islamic State of Iraq and Syria infuriated rebels from a broad spectrum of groups, including the conservative militant Ahrar al-Sham, with whom Suleiman was affiliated, and the Islamic Front coalition, of which Ahrar al-Sham is a member.
Anti-ISIS demonstrations broke out all over the country, and the Islamic Front demanded in statements that ISIS surrender those responsible for killing Suleiman.
It remains to be seen how openly the Islamic Front, which numbers thousands of fighters, will confront ISIS, which has worked closely with rebel groups — including the Islamic Front and Ahrar al-Sham — in the past.
ISIS increasingly has alienated even the pro-rebel population with its austere interpretation of Islamic law and its often-brutal reaction to alleged slights against Islam. But the Islamic Front, Ahrar al-Sham and Syria’s other al-Qaida affiliate, the Nusra Front, generally have downplayed their ideological and tactical differences with ISIS, despite growing insistence by some Syrian rebels that the group is driving support away from them. The United States and Great Britain suspended military support to the rebels after ISIS seized control of rebel warehouses near the border with Turkey.
Islamic Front statements Friday suggested that the group was nearing the end of its patience with ISIS over Suleiman’s killing.
“This ugly act could only have come from souls that were fed lies and are full of hatred,” the statement said. “The Shariah of Allah would never have permitted something like this,” it said, referring to Islamic law.
The group demanded that the perpetrators be brought before an Islamic court.
At the same time, a group of rebels formerly aligned with the now-defunct Free Syrian Army, the U.S.-backed alliance that collapsed late last year, announced that it had formed a new alliance, the Army of the Mujahedeen, that attacked ISIS positions outside the mostly rebel-held city of Aleppo.
The group claimed to have killed numerous ISIS fighters in the battles, including a confrontation around the suburb of Atarib that raged most of Friday.
By early Friday afternoon, activists claimed that intercepted ISIS communications had called on the group’s units to abandon fighting Syrian regime forces and to move to western Aleppo province to fight fellow rebels.
A later statement from the Islamic Front demanded that ISIS stop fighting at Atarib “immediately and stop killing the mujahedeen.” It noted that the groups ISIS was fighting now were the same ones that had seized the area from troops loyal to President Bashar Assad.
“This is exactly what the Assad regime wants,” the statement said.
Aymenn al-Tamimi, who analyzes radical Islamist groups in Syria and Iraq for the Philadelphia-based Middle East Forum, said that while the fighting was spreading around Aleppo it wasn’t yet clear that Ahrar al-Sham and the Islamic Front would join the battle against ISIS.
“I am inclined to see this development as a more localized thing,” he said.