The Al Qaeda-linked Nusra Front and like-minded groups attacked two pro-government and predominantly Shia towns, in Syria's Aleppo province.
The attack on the towns of Nubul and Zahra Sunday was apparently carried out by the militants to connect areas under their control with each other, Xinhua reported, citing a monitoring group.
According to the Syrian Observatory for Human Rights, the terror groups' fighters succeeded to seize control of an area in the southern part of Zahra.
The most fierce clashes erupted when the Nusra fighters attacked the al-Halabi orchard north of Nubul to divert the attention of the National Defence Forces (NDF), a pro-government armed militia.
At least eight Nusra fighters were reportedly killed during the attack, along with an unknown number of the NDF fighters.
The two predominantly Shia towns have for long been besieged by rebel groups, and humanitarian organisations have taken pains to deliver aids there.
The long-running conflict in Syria has pitted the extremist Sunni rebels against other sects, mainly the Shia and its Alawite offshoot.