The eastern part of Aleppo has been besieged by regime forces for months. Now aid agencies fear that thousands of families are at risk of losing their lives.
Why are the civilians fleeing?
Syrian regime leader Bashar al Assad's forces and their Shia militia allies killed 82 civilians including women and children in 24-hour a period between Monday and Tuesday, the United Nations said.
These numbers are based on reports from aid groups working in Syria, but the actual count could be much higher as regime forces take control of remaining neighbourhoods from fleeing rebels.
The UN High Commission for Human Rights said civilians were killed in rebel-held areas such as the al-Kallaseh neighbourhood.
"Civilians have paid a brutal price during the conflict, and we are filled with the deepest foreboding for those who remain in this last hellish corner of opposition-held eastern Aleppo," the commission said in a statement.
How many people remain in the besieged part of the city?
It's difficult to say. The UN Dispatch estimates that 100,000 people were caught in the crossfire. The political office of the Free Syrian Army, a rebel group, said that 150,000 are still trapped inside their homes and unable to leave for fear of being killed.
Breaking: News about Russian agreement to give safe corridor to evacuate 40K civilians from eastern #Aleppo— Asaad Hanna (@AsaadHannaa) December 13, 2016
but ..there is another 100K ppl
Before the civil war erupted in 2011, historic Aleppo was Syria's most populated city and the centre of trade. It was divided into equal parts between the rebels and the regime.
Inside eastern Aleppo, the rebels have been pushed into a very small area that spreads over just a few kilometres. It has been under intense siege as regime forces regularly drop bombs on residential areas.
Thousands of people are too scared to cross over to the regime-held part of the city which has been spared from destructive air bombardments.
Do civilians have a safe place to go?
Hundreds of people have tried crossing over into the regime-held western Aleppo. But it is difficult and dangerous.
Sniper-fire has prevented people from venturing into the streets and risk being injured or killed. There were also reports that regime soldiers have kidnapped young men.
The Russian defence ministry said that more than 13,000 civilians were evacuated from rebel-held areas on Sunday.
Throughout the conflict, Russia has maintained that civilians have been free to leave eastern Aleppo at any time. Opposition fighters said this was untrue.
Turkey is negotiating with Russia to open a corridor to evacuate Syrian rebel fighters and civilians from remaining opposition-held districts of Aleppo, Reuters reported on Tuesday. No agreement has yet been reached.
What's the future of Aleppo's residents?
It is unclear how the regime will treat the tens of thousands of people who remain in the city. Assad has been known to be heavy-handed with his opponents, Faysal Itani, a senior fellow at Rafik Hariri Center for the Middle East, wrote in the New York Times.
A doc in east Aleppo: "A farewell message: Remember that there was a city called Aleppo that the world erased from the map and history."— Kareem Shaheen (@kshaheen) December 13, 2016
In 2014, rebel fighters in Homs surrendered to the regime as part of a truce. "Many were promised amnesty, only to be conscripted into the very military that had killed their families," Itani said.