Syrian government forces have made major gains in southern Aleppo, state media and activists say, leaving rebels with only a small pocket in the city.
“The battle is at its end,” Lt Gen Zaid al-Saleh of the Syrian army said.
An English teacher in the rebel-held enclave told the BBC that people there were facing “doomsday”.
The rebels have now lost more than 90% of the territory they once held in eastern Aleppo in less than a month. Tens of thousands remain trapped there.
They have virtually no food or water.
While many civilians have fled from the enclave into government-held areas, others say they fear they would be killed if they put themselves in the hands of the authorities.
Russia, which backs the Syrian government, says more than 100,000 civilians have been displaced by the fighting – including 13,300 in the past 24 hours – and that 2,200 rebel fighters have surrendered.
Aleppo was once Syria’s largest city and its commercial and industrial hub before the uprising against President Bashar al-Assad began in 2011.
For much of the past four years it has been divided roughly in two, with the government controlling the western half and rebels the east.
Troops finally broke the deadlock with the help of Iranian-backed militias and Russian air strikes, reinstating a siege on the east in early September and launching an all-out assault weeks later.
UK-based monitoring group the Syrian Observatory for Human Rights said the army was on the verge of re-taking all of the east of the city and that rebels had withdrawn from another six neighbourhoods.
The group’s director, Rami Abdel Rahman, told AFP news agency that the areas still under rebel control were “very small” and that “they could fall at any moment”.
In an interview with the BBC’s Victoria Derbyshire programme, English teacher Abdul Kafi Alhamado, who is still inside one of the remaining rebel-held areas, described the conditions as terrible.
“The situation inside the eastern part of Aleppo is literally doomsday,” he said. “Bombs are everywhere, people are running, people are injured in the streets, no-one can dare go to help them, some people are under the rubble.”