At least 35 civilians were killed on Saturday as government forces and rebel fighters exchanged fire in Syria's main northern city of Aleppo, a monitoring group said.
The Syrian Observatory for Human Rights said the dead included 18 civilians -- two of them children -- killed in regime air strikes on Al-Maadi and Sheikh al-Lutfi, two rebel-held neighbourhoods in east Aleppo.
"Seventeen other civilians were killed when rebel groups fired rockets on neighbourhoods controlled by the regime, including Suleimaniyah and other areas," the Britain-based group said.
Pictures circulating on social media depicted significant damage.
Fighting erupted in Aleppo in 2012, reducing swathes of Syria's commercial hub to ruins.
Government forces control the west of the city and frequently bomb rebel-held neighbourhoods in the east from the air.
The rebels often retaliate with rocket and mortar fire into government-held neighbourhoods.
Both sides have been criticised by human rights groups for firing indiscriminately on civilians.