Syrian warplanes carried out air strikes on rebel-held areas in Deraa, Hama and Aleppo provinces and insurgents fired rockets at government targets on Thursday, just as peace talks were set to resume in Geneva after a 10-month hiatus, a war monitoring group said.
However, the overall level of violence in western Syria was somewhat lower than in previous days, the British-based Syrian Observatory for Human Rights said.
In the southern province of Deraa, where clashes have intensified over the past week, Islamist insurgents detonated a car bomb and government helicopters dropped barrel bombs, the Observatory reported.
Government forces meanwhile shelled areas in the northern city of Aleppo's western outskirts, and Syrian jets carried out air strikes around an area where the army and its allies had advanced on Wednesday, the Observatory said.
The Geneva talks are taking place after nearly two months of an increasingly shaky ceasefire between the government and rebels, with each side accusing the other of violations.
President Bashar al-Assad, who is backed by Russia and Iran, has gained the military advantage over the past year. Damascus says all insurgents fighting against it are terrorists.
Hard-line jihadist groups such as Islamic State are excluded from the truce, which took effect on Dec. 30, brokered by Russia and Turkey, which supports the rebels.
A military media unit run by Syria's Lebanese ally Hezbollah said on Thursday that Syrian and Russian warplanes carried out a number of air strikes against Islamic State in the eastern city of Deir al-Zor, most of which the group controls.