Fighters from an al Qaeda splinter group, the Islamic State of Iraq and the Levant (ISIL), withdrew from a rebel-held Syrian town near the border with Turkey on Friday, a monitoring group said.
Months of rebel infighting in and around Azaz, 5 km (3 miles) from the Turkish border, has hampered efforts to get humanitarian aid into Syria and help tens of thousands of refugees who fled there to escape bombardment by government forces in Aleppo province.
ISIL, which took Azaz five months ago from rival opposition fighters, has fought other rebels who control the border post with Turkey. A car bomb last week at a makeshift camp on the Syrian side of the border killed five refugees.
The Britain-based Syrian Observatory for Human Rights, which reported the withdrawal, says 3,300 people have been killed since the start of the year in fighting between rebel factions trying to overthrow Syrian President Bashar al-Assad.
Rami Abdulrahman, head of the anti-Assad Observatory, said ISIL withdrew at dawn to strongholds east of Aleppo city. He said the group was suffering heavy losses in Azaz.
The infighting started last year over power struggles and territorial disputes and has since spread throughout rebel-held territory in Syria.
A peaceful protest movement against four decades of Assad family rule in 2011 turned into civil war after a government crackdown. More than 140,000 people have been killed, according to the Observatory.