Ahrar al Sham and Nureddine al Zinki rebel groups announce the formation of the Syrian Liberation Front in the northwest of the war-torn country.
Two Syrian rebel factions announced they were merging on Sunday, in an apparent attempt to pre-empt a broader clash with Al Qaeda-linked militants in the country's fractured northwest.
"We, Ahrar al Sham and Nureddine al Zinki, announce our merger under the Syrian Liberation Front," the two groups announced.
Ahrar al Sham commander Hassan Soufan will become the leader of the new joint force, while Nureddine al Zinki commander Tawfiq Shahabuddin will serve as his deputy, Anadolu Agency reported.
Both groups have a strong presence in rebel-held parts of the country's north, along the border between the provinces of Aleppo and Idlib.
Idlib province is held mostly by Hayat Tahrir al Sham (HTS), an alliance dominated by militants once linked to Al Qaeda.
In their founding statement, the Syrian Liberation Front called on rebel groups to join their new movement.
Sam Heller, a senior analyst at the International Crisis Group, said the merger was linked to HTS's growing power in northern Syria.
"This is an attempt to form a counterweight to Hayat Tahrir al Sham, which is apparently positioning itself for a new fight with Zinki," he told AFP.
"Zinki and Ahrar are the two most substantial non-jihadist factions in the rebel-held north, and Zinki in particular has been an obstacle to Hayat Tahrir al Sham's attempts to consolidate control."
Syria's conflict erupted in 2011 with protests against the regime of Bashar al Assad, but it has since evolved into a complex war.
The opposition movement has long been fractured, but mainstream rebels have struggled in recent years to fight off the influence of powerful factions like HTS.