The Syrian Observatory for Human Rights said yesterday's toll, up from an earlier figure of 16 killed, was one of the heaviest since the regime launched an offensive on eastern Aleppo on November 15.
"There was an escalation in the evening, with successive bombardments," Observatory head Rami Abdel Rahman told AFP, adding that many people were trapped under rubble.
"There are many wounded people, and bodies, still trapped under the rubble," he said, adding that several neighbourhoods had been hit across insurgent-controlled neighbourhoods.
The reporter was able to travel to Al-Mashad neighbourhood where he saw rescuers sifting through the rubble of a building that had been hit, working in total darkness.
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Three floors were flattened, the reporter said, adding that the building was located on a street that has been targeted in the past.
"We didn't realise what happened. Everything just came down all around us," said resident Ahmad.
At least 188 civilians, including 27 children, have been killed since the assault was launched on November 15, according to the Observatory. Rebel fire has killed 16 civilians in the government-held west, including 10 children.
Earlier in the evening, Bab al-Nayrab, another neighbourhood in eastern Aleppo, was badly hit by what rescuers said was a barrel bomb dropped by a government helicopter.
An AFP cameraman captured video footage of rescuers battling from more than one hour to pull a seriously wounded boy from the rubble of a building.
The lower part of the boy's body was stuck in the rubble and a bloodied gash could be seen at the back of his head as if part of the scalp had been ripped apart.
The boy, who could be heard crying out "Father, Father" as he pleaded for them to hurry up and get him out, was lifted alive from the rubble.
"The operation took us an hour, an hour and a half... And there is still a woman trapped under the rubble," one of the rescuers told AFP.
Since November 15, government forces have pounded eastern Aleppo with air strikes, barrel bombs and artillery fire in a bid to retake that part of the city from insurgents.