At least 20 people were killed Monday in rebel shelling on government-held areas of the northern Syria city of Aleppo and in a car bomb attack on an army government checkpoint on the outskirts of Damascus, state media and a monitoring group reported.
State news agency SANA said that 15 people were killed in the shelling in Aleppo, with another 81 injured.
The agency said the attacks had been carried out by Syrian al-Qaeda affiliate the al-Nusra Front and associated groups. The opposition Syrian Observatory for Human Rights said that Islamist factions had carried out the shelling.
The Observatory put the death toll at 19, and added that another 15 people had been killed in rebel shelling in the city over the previous three days.
Aleppo, Syria's largest city before the war, is divided between a government-held western sector and the rebel-held east.
Government advances in recent months, backed by Russian airstrikes, have put the east - already devastated by years of shelling and air raids - at risk of encirclement and siege.
In the Damascus suburb of Sayyida Zeinab, a regime stronghold, the Observatory reported that eight people were killed in a car bomb attack at an army checkpoint.
State news agency SANA put the number killed at only five, but said 20 others were wounded "by the terrorist bombing."
It said that a suicide attacker blew up his four-wheel-drive vehicle after he was discovered by one of the soldiers manning the checkpoint just south of Sayyida Zeinab.
The area is home to an important Shiite shrine. Pro-Iranian militias who have come to the aid of overstretched Syrian government forces have boasted that they are defending the shrine.
Deadly bomb attacks on checkpoints in Sayyida Zeinab in January and February that were claimed by the Islamic State extremist group killed almost 200 people, including more than 100 civilians, according to reports from the Observatory at the time.
In Geneva, the head of the Syrian regime delegation Bashar al-Jaafari said the bomb attack "is a proof that those who claimed they were having dialogue with us here in Geneva diplomatically and then decided to withdraw ... are no more than terrorists and terrorism sponsors."
He was referring to the Syrian opposition delegation, which decided last week to postpone the talks in Geneva until the shelling stops on rebel-held areas across Syria.