The Local Coordination Committees in Syria, the group that speak for the rebels, said Thursday that at least 20 people were killed and more than 80 wounded in an airstrike in a residential area, the Al-Ansari district in Aleppo.
Most of the wounded were children, they said.
An anti-Assad activist in Aleppo uploaded videos of the attack. One shows children being dug out of rubble and rushed away. In another video on older man appears dazed as he carries the remains of a bomb.
He says: "This is a gift from Bashar to the people of Al-Ansar district. Look at the building over there. Two floors have been destroyed, and this is part of the rocket that destroyed these buildings."
Rebels claim to shoot down military aircraft
On Wednesday, villagers in northern Syria picked pieces of a downed fighter jet from an olive grove after rebel fighters claimed to have shot down three government aircraft in 24 hours.
Al-Assad's government has relied increasingly on air power to battle the 21-month-old revolt against it, and witnesses said a cheer went up when the jet went down near Aleppo.
"We want to take this ... to show them in the other villages," a man who identified himself as Abu Dargham told CNN as he showed off two twisted chunks of metal. "Let them see what happened to these planes."
The downed plane's tail was largely intact, but the fuselage was in pieces and the type of aircraft was not immediately identifiable. Locals picked it apart, some of them stuffing pieces into bags as a tractor hauled away what appeared to be an engine. Cheering children were piled on the tractor as it drove away.
Witnesses said two fliers ejected from the plane before the crash. One was found unconscious and taken to a makeshift clinic, while villagers said they were still searching for the other late Wednesday.
Rebels posted two videos online to support their claims. One shows rebels carrying an unconscious man wearing what looks like a military pilot uniform, while another includes footage of medics bandaging a bloodied and moaning man.
"Here is the pilot who was shelling houses of civilians!" someone says off-camera. "The heroes of Darret Ezza shot down his plane!"