The Syrian army clashed with rebels near the main military airport in Damascus and shelled the northern hub of Aleppo, a watchdog said, as the country braced for protests after Friday Muslim prayers.
The fresh violence was reported after a day which saw 180 people killed across the country, the majority of them civilians, the Syrian Observatory for Human Rights said. The Observatory also reported that the bodies of 65 unidentified people were found in Qatana, a town southwest of Damascus, without providing further details about the dead.
Fighting erupted between regime forces and rebel fighters near Mazzeh military airport on the western outskirts of the capital, according to the Observatory which has a network of activists on the ground.
According to the Syrian Revolution General Council opposition faction, fighting also raged through the night and into the morning in a string of southern neighbourhoods of Damascus.
"The sound of shelling and clashes hardly stopped, as helicopters and tanks shelled the area at random, and hysteria broke out (among residents)," the SRGC said.
The Britain-based Observatory also reported clashes on the highway between Damascus and the southern province of Daraa, where it said two boys were killed in an army ambush.
It further reported that several southern districts and outlying areas were shelled by the army, while combat helicopters bombarded a green area near the upscale western neighbourhood of Mazzeh, where shooting broke out Wednesday near the prime minister's office.
In the embattled northern city of Aleppo, which has emerged as the key battleground in the escalating conflict, several rebel-held districts came under bombardment by government forces.
Outside Aleppo, the army reportedly regained control of the town of Al-Tal, which the opposition Syrian National Council described on Tuesday as a "disaster area" after nearly a week of shelling.
Elsewhere, five civilians were killed in army gunfire and a rebel died in clashes in the eastern province of Deir Ezzor along with four soldiers, bringing Friday's initial toll to 12 killed, the Observatory said.
Meanwhile, activists called for Friday demonstrations under the slogan "If our Free Army is united, victory is assured".
More than 23,000 people have died in Syria since the revolt against the regime of President Bashar al-Assad broke out in March 2011, according to the Observatory, while the UN puts the toll at around 17,000.