Clashes have broken out in Damascus, with Syrian government forces firing mortar rounds on rebel positions, activists say, in what they describe as some of the heaviest fighting in the nation's capital this month.

The violence on Thursday coincided with the departure from the country of UN monitors, whose mandate expired and was not renewed due to deteriorating conditions that have dragged Syria into civil war.

Al Jazeera's Rula Amin reports from Beirut.