The UN Security Council is meeting to discuss the sitution
Syrian rebels and civilians will be evacuated from the small part of Aleppo still under their control, as Russia claims all military operations in the city have ended.
A ceasefire has been agreed and buses will start to take people out at 5.00am (3.00am GMT), a military source told the Reuters news agency.
The UN envoy to Syria, Staffan de Mistura, confirmed the evacuation was "imminent".
The announcement came as insults were exchanged at an United Nations emergency session - convened over reports of government troops and allies killing civilians "on the spot".
Russia's ambassador to the UN told the meeting: "According to the latest information that we received in the last hour, military actions in eastern Aleppo are over."
Vitaly Churkin also claimed only fighters would be leaving the city as "nobody is going to harm the civilians".
President Assad's forces, backed by Russia and other groups, have recaptured large areas of eastern Aleppo in recent days.
According to state TV, they now hold 98% of neighbourhoods previously occupied by the rebels..
Tens of thousands of civilians remain trapped in the east of Aleppo, including more than 100 unaccompanied children inside a building that was under heavy attack, according to UNICEF.
The UN human rights office said it had reports of pro-government forces killing at least 82 civilians in eastern Aleppo, including 11 women and 13 children in four different neighbourhoods.
"The reports we had are of people being shot in the street trying to flee and shot in their homes," UN humanitarian spokesman Jens Laerke told reporters.
He said the situation appeared to be "a complete meltdown of humanity".
The White Helmets, the volunteer search and rescue force, tweeted: "+100,000 civilians are packed into a tiny area. Bombing + shelling relentless. Casualties unimaginable. Bodies lie where they fell."
The atmosphere at the UN's emergency session was especially tense, with diplomacy replaced by insults and accusations.
Outgoing Secretary-General Ban Ki-moon said the council has "not exercised its preeminent responsibility":
Aleppo: Ban Ki-moon says Security Council has not exercised its preeminent responsibility w/ regard to maintenance of intl peace & security. pic.twitter.com/eEH7NJd1r6— United Nations (@UN) December 13, 2016
The bluntest exchange was when the US ambassador to the UN, Samantha Power, looked directly at her Russian counterpart and told him: "You will be not absolved of these massacres. Aleppo will define modern evil and will stain our conscience decades later.
"It should shame you. Is there nothing that could shame you? Is there nothing you will not lie about?".
The Russian ambassador retorted that she was behaving "like Mother Theresa" and accused the US, UK and France of distributing fake news about the crisis.
Russia has vetoed the last six UN resolutions aimed at easing the dire situation in Aleppo.