World Bulletin / News Desk
Forces loyal to President Bashar al-Assad have in some cases entered homes and killed those inside, and in others "caught and killed on the spot" fleeing civilians, Rupert Colville, the UN rights office spokesperson, said on Tuesday.
He called the situation "a complete meltdown of humanity".
Colville said government forces on Monday killed 82 civilians - including 13 children and 11 women - in the neighbourhoods of Bustan al-Qasr, al-Kalleseh, al-Firdous and al-Salheen - taken over that day by government forces.
Fears have been growing for thousands of trapped civilians as the rebels make a desperate last stand in their remaining pocket of territory in the former opposition stronghold of east Aleppo.
The Syrian army said on Tuesday evening it could declare full control over east Aleppo "at any moment" as it advanced against rebels holed up in just a handful of neighbourhoods.
About 80,000 civilians are now trapped in the few square miles of east Aleppo that remain under opposition control.
Witnesses described scenes of carnage in previously opposition-held areas, with bodies lying amid the rubble of eastern Aleppo's streets as desperate residents sat on pavements with nowhere to shelter.
"Our fate is sealed. Why would we hide? It won't do us any good. We will either die or be captured," said Ibrahim Abu al-Laith, a spokesman for the White Helmets rescue service.
Jan Egeland, UN special adviser for Syria, said the past 24 hours had been the most dramatic so far in "the bloody, bitter, horrific battle for Aleppo".
He gave warning that those responsible would be held accountable for the bloodshed.