Rebels backed by Turkey sent reinforcements to counter a Syrian army campaign in the northwestern province of Idlib on Sunday, a war monitor reported, according to the Xinhua news agency.
A total of 140 military vehicles were sent from positions held by the Turkish-backed National Army rebel group in northern Aleppo province to rebel positions in Idlib.
The Syrian Observatory for Human Rights said Russian warplanes carried out 11 airstrikes on rebel positions in Idlib on Sunday.
The strikes targeted Maarat al-Numan and surrounding areas in Idlib.
It said the Syrian forces also shelled rebel-held areas in the southern Idlib countryside.
The Syrian army has made notable progress in recent weeks in the battles against the rebels in Idlib, capturing several areas in the quest to liberate the road linking Hama province with Aleppo in the north.
Certain parts of Idlib are included in a de-escalation zone’s deal brokered by Russia and Turkey, which backs the rebels.
However, such deals exclude the ultra-radical rebels who are affiliated with al-Qaeda and are branded as terrorist groups by the UN.