Fighting erupted overnight near the Hanano barracks in the Arkoub district of northeast Aleppo, the Syrian Observatory for Human Rights said.
Two weeks ago, rebels stormed the Hanano base -- perched on a hill and near the regime-controlled citadel that dominates the city -- but were outgunned by the army and pushed out after three days of fierce battles.
Several districts of the northern metropolis, including Sakhur in the northeast and Bustan al-Qasr in the centre, came under overnight attack, the Britain-based watchdog said.
Elsewhere in the northern province, fighting broke out between troops and rebels near the Meng military airport, the watchdog said.
Military airports have been a key target for the rebels as the army has increasingly deployed warplanes and helicopter gunships to launch devastating strikes against them.
Northwest of the capital Damascus, the Observatory reported a massive explosion, believed to be a car bomb. Heavy gunfire was heard afterwards but there were no immediate reports of casualties.
In the central province of Homs, a civilian was killed in dawn shelling of Rastan, while the eastern city of Deir Ezzor and the town of Daal in the southern province of Daraa also came under bombardment.
On Thursday, at least 225 people -- 140 civilians, 39 rebels and 46 government troops -- were killed nationwide, according to the Observatory.
The dead included 25 civilians killed in Aleppo.
And at least 30 civilians were reported killed on Thursday in a massive explosion at a petrol station in the northeastern province of Raqa.
Activists said the petrol station, in the village of Ain Issa, was hit by a warplane.
