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.
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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.