Fierce clashes raged between the government forces and insurgents of the “Army of Conquest”, a coalition of groups that includes Nusra Front and Ahrar al-Sham, the Observatory said.

Insurgents detonated at least five car bombs and fired 370 rockets at two Shiite villages in northwestern Syria on Friday, a monitor said, in a new assault on besieged government-held areas.

An alliance of insurgent groups, including al-Qaeda’s al-Nusra Front, attacked al-Foua and Kefraya in Idlib province, an area bordering Turkey that is mostly held by insurgents after rebel advances this year, the Syrian Observatory for Human Rights said.

Thousands of civilians have been living under siege in the two villages, which are still held by government forces.

Fierce clashes raged between the government forces and insurgents of the “Army of Conquest”, a coalition of groups that includes Nusra Front and the powerful Ahrar al-Sham, the Observatory said. The number of casualties was not immediately clear.

Warring sides agreed to a brief ceasefire last month in the two villages and in Zabadani, a rebel-held town near the Lebanese border under siege by government forces and by Lebanese Shiite group Hezbollah, a Damascus ally.

But the two-day ceasefire, the second that month, collapsed before wounded people could be evacuated from both areas.

Government forces have since intensified their assault on Zabadani and say they are on the verge of seizing the town, where insurgents are holed up in its centre.