Syrian troops bombarded southern districts of Damascus and the outskirts of the capital before dawn, according to the Syrian Observatory for Human Rights and activists on the ground.
Residents in Damascus were kept awake through the night with the sound of explosions rumbling in the capital, they told AFP.
The eastern outskirts of Damascus, a key bastion of rebel fighters, were particularly hard hit. The Observatory reported fierce shelling in Douma, Madamiyeh al-Sham, Irbin and the Eastern Ghouta region.
The Britain-based watchdog also reported heavy bombing in the southern districts of the capital, including in Hajar al-Aswad, Tadamun and the Yarmuk Palestinian refugee camp.
"Fierce shelling has resumed in Hajar al-Aswad and more than 20 shells have hit the district so far," reported the Local Coordination Committees, a network of opposition activists on the ground.
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A massive military operation and fighting to the east and south of Damascus left 39 people dead on Thursday, according to the Observatory, which relies on a network of activists, lawyers and medics in civilian and military hospitals.
In the northern city of Aleppo, troops and rebels clashed near Nayrab military airport, which has been under regular rebel attacks for the past several months.
Battles and shelling carried on through the night and into the early morning in several districts of Aleppo, once Syria's thriving commercial hub, the Observatory said.
In the central province of Homs, the army attempted to storm the rebel stronghold of Rastan from the north and fierce clashes broke out as rebels blocked the incursion.
Homs has suffered some of the worst bloodshed and destruction of the uprising against President Bashar al-Assad's regime as the army has mounted repeated attempts to recapture rebel-held areas.
On Thursday, 121 people -- 50 civilians, 39 rebels and 32 loyalist troops -- were killed across Syria.