Opposition fighters on Monday (July 11th) launched an assault on regime-held districts in Syria's Aleppo after the regime severed their only remaining supply route into the city, AFP reported.

The opposition offensive began at dawn, with heavy clashes between regime and opposition forces along the front line of the northern city.

"Opposition factions launched a wide-scale attack on four fronts against the regime inside Aleppo city, including in the Old City," said Syrian Observatory for Human Rights chief Rami Abdel Rahman.

"There is currently fierce fighting under way, but the opposition has not advanced because of the heavy aerial bombardment the regime is carrying out," he said.

Bombardment of the opposition-held part of the old city left three civilians dead Monday morning, the Observatory said, while a barrage of 300 opposition shells had been fired into western Aleppo since dawn, killing nine civilians.

On Sunday, opposition fighters launched an assault to push regime forces back from the Castello Road and reopen the main supply route, but it failed and ended with at least 29 opposition fighters dead.