Fierce clashes raged on Tuesday inside the historic Umayyad Mosque in Syria's second city Aleppo, as rebels battled troops at a police academy elsewhere in the province, a watchdog said.
The Syrian Observatory for Human Rights said rebels had pushed into the regime-held mosque from their positions at the southern entrance, and were also fighting troops in the UNESCO-listed Old City.
A military source earlier reported heavy fighting and said rebels had detonated an explosive near the southern outer wall of the mosque to break into the courtyard.
In October, the mosque was heavily damaged when a fire broke out amid clashes and charred several antique furnishings and one of its intricately sculpted colonnades.
Elsewhere in Aleppo province, rebels pushed into the grounds of a major police academy and seized one of its buildings after a fierce two-day siege in which more than 70 combatants were killed, the Observatory said.
The academy, located near the town of Khan Assal, is one of the last regime bastions in the province.
A second military source said rebels were blockading the entrance of the school and clashes were continuing on the periphery.
"We called for reinforcements yesterday and they have still not arrived," he told AFP on condition of anonymity.
Regime forces retaliated with air strikes on rebels around the school and reinforcements were seen heading towards Khan Assal, according to the watchdog, which collects its reports from a network of activists and medics on the ground.
Air strikes were also reported in the southern province of Daraa, the eastern outskirts of Damascus, the northwestern province of Idlib, the northern province of Raqa and the eastern city of Deir Ezzor.
An AFP correspondent in Deir Ezzor said two MiGs flew repeated low-level sorties over the Sheikh Yassin neighbourhood for more than three hours during the morning, droping at least 50 bombs on rebel positions.
The strikes were accompanied by shelling from light and heavy artillery, as troops tried to open a breach in rebel defences.
"They have been preparing an offensive for a week and have been moving troops in the enter the neighbourhood," local rebel commander Khaled bin al-Walid said.
In Damascus, three young children were killed by army shelling on the eastern district of Jobar, the Observatory said, giving an initial toll of 59 people killed nationwide on Tuesday.