Six powerful Syrian rebel groups on Thursday demanded al Qaeda-linked militants and rival insurgents end clashes that have escalated infighting in a strategic northern border area.
The al Qaeda-affiliated Islamic State of Iraq and the Levant (ISIL) seized Azaz, about 5 km (3 miles) from the frontier with Turkey, last month and has repeatedly clashed with the local Northern Storm brigade since then.
A previous attempt by rebel groups to broker a truce between the two sides failed.
The fighting prompted Turkey to close its border crossing, a lifeline for Syria's rebel-held northern areas because it let refugees out and supplies like food and building materials in.
A statement by activists on Thursday called for an immediate ceasefire between the two sides and called on them to submit their dispute to an Islamic court in Aleppo, about 30 km (20 miles) to the south.
"We ask our brothers in the faction of the Islamic State of Iraq and the Levant to withdraw their forces and equipment to their essential bases immediately," the statement said.
"We consider them above spilling the blood of Muslims or rushing to describe them as infidels and apostates."
The statement was signed by commanders from the powerful Ahrar al-Sham, Liwa al-Tawheed, Suqour al-Sham and Army of Islam brigades, and a copy was posted to Northern Storm's Facebook page. It did not say what the groups would do if the two sides did not stop fighting or if ISIL did not withdraw.
"This was a declaration signed by the biggest rebel brigades in Syria. The message is clear," an official in Ahrar al-Sham, who did not want to be named, told Reuters.
Rebel divisions have hurt their fight against President Bashar al-Assad's better equipped and organized forces in the 2-1/2-year-old conflict. Tensions have been rooted partially in conflicting ideologies, but more often in disputes over resources, territory and spoils of war.
Also on Thursday, activists in the rebel-held city of Raqqa to the east accused ISIL fighters of smashing a statue of an early Islamic leader because they considered it idolatrous, the Britain-based Syrian Observatory for Human Rights reported.
ISIL released an audio recording this week accusing Northern Storm of provoking the fighting in Azaz.
Separately, a video posted online showed rebel commanders in Rastan, a town in the outskirts of the central city of Homs, rejecting the presence of ISIL and the Nusra Front, another al Qaeda-affiliated faction, in the area.
Again, it was not clear what action they would take if the Islamists did not leave the area.
Rebel infighting has worked to Assad's advantage. Just over a month ago, the government faced the possibility of military action by the United States, but the threat was averted by a deal to eliminate the country's chemical weapons.
A team of experts charged with starting that process arrived in Damascus on Tuesday for the U.N. Security Council-endorsed mission and is expected to begin inspections next week.