BEIRUT (Reuters) - Syrian government forces and their allies battled insurgents including al Qaeda fighters in fierce clashes south of Aleppo late on Saturday, and the rebels advanced taking over two hilltops, the Syrian Observatory for Human Rights said.
The Britain-based monitoring group's director Rami Abdulrahman said this might mark a breakdown in the area of a fragile cessation of hostilities agreement which has been in place for several weeks and slowed fighting but not halted it.
Insurgent fighters including those from the al Qaeda-affiliated Nusra Front had earlier begun an assault nearby and southwest of Syria's former commercial hub Aleppo, the Observatory said.
Syrian and Russian warplanes launched dozens of air strikes in the area, it said.
The Russian- and U.S.-brokered ceasefire agreement excludes al Qaeda and Islamic State.
Fighting has continued against Islamic State, and between Syrian government forces and other rebel groups in some areas in the west of the country.
Warring sides in the conflict have traded blame for violations of the truce.
(Reporting by John Davison, Editing by Franklin Paul)