Hundreds of Syrian civilians have fled into government-controlled areas of Aleppo as troops make advances against rebels in the east of the city.
The move to western Aleppo came after troops retook Hanano district, the largest controlled by the rebels.
The capture of Hanano gives the army an advantage in its drive to seize other opposition-held areas.
Some 275,000 people are under siege as the army’s offensive – now in its 13th day – is intensified.
The assault has killed 219 civilians, the UK-based Syrian Observatory for Human Rights says.
Among the victims were 27 children, the monitoring group added. Reports suggest there is a lack of medical supplies and food.
Meanwhile, rebels have intensified rocket attacks on the government-controlled western districts of Aleppo. Their attacks have killed 27 civilians since the offensive began, the Observatory said, including 11 children.
The Syrian army’s success in Hanano is its biggest of the offensive against the rebels.
Retaking all of Aleppo would be a major victory for Syrian President Bashar al-Assad after five years of conflict.
Hanano was the first neighbourhood in Aleppo taken by rebels in 2012.
Syrian forces regained the district on Saturday – a move making it easier for them to isolate the northern districts of east Aleppo from the southern ones.
Air strikes launched as part of the recent government offensive were described by activists as the most intense ever, leaving the streets deserted.
As the army advance neared, the Observatory said more than 400 residents had left the eastern districts of Haidaria and al-Shaar, where they were received by the army and taken to areas under their control in the west of the city.
Al-Jazeera says others are moving out of the besieged neighbourhoods of Hulluk, Sheikh Fares and Sakhour.
Civilians in eastern Aleppo had until now rejected several government ultimatums to leave and the latest development is important, says the BBC’s Sebastian Usher.
Aleppo, once Syria’s commercial and industrial hub, 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.