Syrian rebels battled army units for control of districts of Damascus for a second day yesterday, part of a rebel offensive which aims to shake President Bashar al-Assad’s hold on the capital, a rebel captain and opposition activists said.

Units of Assad’s elite Republican Guard based on the imposing Qasioun Mountain overlooking the city fired artillery rounds and rockets at the eastern neighbourhood of Jobar and at the southern ring road, where rebels have overrun roadblocks and army positions, the sources said.

Assad, battling to crush a 22-month-old uprising in which 60,000 people have died, has lost control of large parts of the country but his forces, backed by air power, have so far kept rebels on the fringes of the capital.

Syrian state media said six people, including a woman and three children, were killed by rebel mortar fire on a bus station in the north-eastern district of Qaboun yesterday, with several other people seriously wounded.

Activists put the overnight death toll in the city at 30 people, mostly from heavy army bombardment on the contested neighbourhoods of Jobar, Zamalka and Hajar al-Aswad. Damascus residents, long accustomed to the sounds of war, said Wednesday’s barrage some of the heaviest they had heard.

Jobar and Zamalka are situated near security compounds housing forces from Assad’s Alawite sect, an offshoot of Shi’ite Islam that has dominated power in Syria since the 1960s. Hajar al-Aswad is close to the southern entrance of the capital and the main highway to the city of Deraa and the Jordanian border.

“Jobar is the most contested district and the regime is bombarding it heavily,” said Captain Islam Alloush of the Liwa al-Islam rebel unit. He said the army was massing forces to take back a major junction on the ring road.

An opposition activist in Damascus said the offensive was being led by Sunni officers who had defected from the army, and aimed to cut Assad’s command and control lines from the centre of the city to its outskirts.