Hayat Tahrir al-Sham (HTS) is on alert, amid concerns of an imminent offensive in northern Idleb province following violations of the Russian-brokered buffer zone agreement, sources said.
All the formations and units of HTS, an alliance led by Syria's former al-Qaeda branch, and which is the dominant force in Idleb, have been mobilizing units.
A statement issued by HTS accused regime forces of breaching the cease-fire, through unprecedented attacks on the northern countryside of Hama and Idleb province that left casualties, including 10 civilians.
The de-militarized zone was announced by rebel backer Ankara and Damascus ally Moscow in September, and separated regime troops and rebel fighters in Idleb and adjacent areas.
Under the deal, the rebels were supposed to have removed all heavy weapons from the buffer zone by Oct. 10, 2018, but skirmishes have continued to pit regime forces against militants and other insurgents on the ground.
Rebel factions have said they withdrew their heavy weapons from the zone but HTS and other hardline groups have refused to pull out their fighters.
On Saturday, HTS fighters killed at least eight regime troops in the north of Hama province, near the planned buffer zone of Idleb.
The deadly militant assault came hours after regime troops killed 23 fighters of a formerly US-backed Jaish al-Izza group inside the planned buffer zone.
Regime forces pushed into the Jaish al-Izaa stronghold, near the town of al-Latameh.
On Wednesday, rebels retaliated by wounding nine regime soldiers in a rocket attack on the Joureen military camp, local activists said.
Idleb and some adjacent areas are the last major rebel bastion in Syria, with all former territories now under the control of the Russian-backed government.
It threatened to assault the rebel territory around Idleb, which is home to some three million people, but a truce deal struck by Russia and Turkey averted the onslaught.
Aid organizations warned that a fully-fledged offensive on Idleb could spark the worst humanitarian catastrophe of the civil war.
More than 470,000 people have been killed and millions displaced since the conflict erupted with the brutal repression of anti-government protests in 2011.
This article was edited by The Syrian Observer. Responsibility for the information and views set out in this article lies entirely with the author.