Meanwhile, 11 people were killed in western parts of Aleppo, with Syrian news agency SANA blaming al-Nusra
At least 20 civilians were killed late on Wednesday in government strikes on a hospital and nearby residential building in the Syrian city of Aleppo, civil defence volunteers known as the White Helmets said.
A dentist and five members of a family, including two children, were among those killed "by air strikes targeting al-Quds Hospital and a nearby residential building in al-Sukkari neighbourhood in eastern Aleppo," the volunteers told AFP.
A doctor who was the only paediatrician in the rebel-held eastern neighbourhoods of Aleppo was also among the dead, an AFP correspondent on the ground said.
The UK-based Syrian Observatory for Human Rights monitoring group confirmed the raids were carried out by "regime airplanes" and said two hospital guards and a doctor were among the dead.
Video footage filmed by AFP showed images of the badly damaged hospital, aid workers transporting the victims in ambulances and a weeping man holding a child.
Rescuers were at the scene searching for victims trapped under the rubble, the AFP correspondent said.
Separately, 11 people were killed in western parts of Aleppo earlier on Wednesday, according to the Syrian Observatory. State news agency SANA blamed the rocket and gunfire on al-Qaeda affiliate al-Nusra Front and its allies.
Also earlier in the day, five civilians were killed in two neighbourhoods in eastern Aleppo, according to the White Helmets. An AFP correspondent said that a government aircraft targeted one area with barrel bombs and another with missiles.
Following a lull in fighting after the ceasefire took effect on 27 February, violence has intensified in recent days, with more than 100 civilians reported dead in air strikes, shelling and rocket fire since Friday.
Once Syria's commercial hub, northwestern Aleppo has been divided between rebel control in the east and government forces in the west since 2012.
The fighting has put the ceasefire in jeopardy and overshadowed a new round of UN-brokered peace talks in Geneva that were entering a recess on Wednesday.
More than 270,000 people have been killed in Syria and millions been forced from their homes since the conflict erupted in 2011.