Thousands of civilians have left rebel-held eastern Aleppo districts, as the Syrian army continues its offensive to take full control over the city.
The Syrian Observatory for Human Rights said as many as 10,000 residents fled to government-controlled western areas and a Kurdish-run northern district.
Syrian state media put the number at more than 1,500, while Russia said that 2,500 civilians had left.
The army wants to split the rebel-held east, after seizing several districts.
It is hard to get a clear picture of how events are unfolding in eastern Aleppo, but it is being reported that:
Government forces have made inroads into Sakhour neighbourhood
The army has taken the district of Holok, according to Reuters news agency
Government forces have also seized Baadeen, Jabal Badra, Inzarat, al-Sakan, al-Shaabi and Ain al-Tall, according to the UK-based observatory
The army took control over Hanano district on Saturday
Seven-year-old Bana Alabed, who has gathered thousands of Twitter followers with her tweets from Aleppo, said on Sunday that her home in the east of the city had been bombed.
She tweeted hours earlier: "Last message - under heavy bombardments now, can't be alive anymore. When we die, keep talking for 200,000 still inside. BYE.- Fatemah"
Ishmael, a volunteer with the White Helmet civil defence non-governmental organisation in eastern Aleppo, told the BBC that Sunday was "the worst day ever in Aleppo... because of the bombing".
Ishmael said more than 20 people had been killed, adding: "I'm scared, really scared of what is going to happen... tomorrow".
Some 250,000 people are believed to remain in eastern Aleppo, where food and medical supplies have all but run out.
Retaking all of Aleppo would be a major victory for Syrian President Bashar al-Assad after five years of conflict.
Once Syria's commercial and industrial hub, Aleppo has been divided roughly in two since 2012, with the government controlling the west and rebels the east.
In the past year, Syrian troops have broken the deadlock with the help of Iranian-backed militias and Russian air strikes.
Russia says its air force is active in other parts of the country, but not operating over Aleppo.