At least 38 civilians were killed and dozens more wounded in fresh violence in Syria's second city Aleppo on Thursday, a monitoring group said.
Rebel rocket and artillery fire on government-held neighbourhoods killed 18 civilians, the Syrian Observatory for Human Rights said.
Two children were among the dead, and about 40 people were wounded.
Regime air strikes on rebel-held districts, including the heavily populated Bustan al-Qasr neighbourhood, killed 20 civilians, the Observatory said.
An upsurge in fighting in Aleppo, Syria's pre-war commercial hub, has killed at least 186 people since Friday, the Britain-based group said.
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An AFP correspondent in the city said the barrage of air strikes began at around 10 am (0700 GMT) and was carrying on into the afternoon.
Rescue workers in the city -- known as White Helmets -- said they were exhausted by the escalation in violence.
"We were still working on the air strikes from last night in the Sukkari neighbourhood," one volunteer told AFP.
Overnight raids on the rebel-held neighbourhood hit a hospital and a nearby block of flats killing at least 30 people, the White Helmets said.
Among the dead was the last paediatrician still working in rebel areas of the city.