Syrian opposition militants ousted an Al-Qaeda-linked faction from one of its northwestern bastions .
Militants from Islamists to relatively secular moderates have been fighting the Islamic State of Iraq and the Levant (ISIL) faction in the worst internecine violence to break out since Syria's crisis began in 2011.
The fighting since the start of January has killed over 1,000 people, according to opposition observatory .
On Friday, the Observatory and activists said ISIL had pulled out of the northern town of Saraqeb, strategically important because it straddles highways connecting Aleppo, the capital Damascus and the coastal city of Latakia.
The Britain-based Observatory said "they burned their cars before the withdrawal and pulled out after covering fire from a brigade loyal to them".
Rival militants- including many from the so called Islamic Front had been fighting to take the town for days and moved tanks and machinegun-mounted pickups against ISIL about a week ago.
A Saraqeb-based activist said ISIL's position weakened when an allied brigade pulled out to protect the nearby town of Sarmin, also under siege by the Islamic Front.
A local commander of the al-Nusra Front - another al Qaeda-linked group which has clashed with ISIL in some areas - said fighters from al-Nusra and from the so called Syrian Revolutionaries Front, yet another grouping in the fractured insurgency, would take over military sites and checkpoints while ISIL and the Islamic Front would withdraw.
The claim of an agreement made by al-Nusra commander was repeated by the Saraqeb-based activist, but other activists disputed it and it was not immediately possible to verify it independently.
The internal militant fighting broke out in earnest at the start of January after months of increasing tensions.
Local resentment toward ISIL, a reinvigorated version of al Qaeda in Iraq, had been growing over their kidnapping and killing of opponents and attempts to impose an uncompromising interpretation of Islamic law in territory under their control.
ISIL, which draws strength from a core of battle-hardened foreign Islamists, also angered fellow militants by seizing territory from rival groups. But the group's loss of Saraqeb, while significant, is unlikely to bring the fighting much closer to an end.
ISIL still controls large amounts of territory across northeastern Syria including Raqqa, the only major city under full militant control.
The group has fended off rival advances with a campaign of car bombs and suicide attacks. ISIL detonated four car bombs against its opponents on Thursday alone and at least one on Friday, according to the Observatory.