Nearly 10,000 civilians flee eastern Aleppo as government retakes areas held by rebels.

Nearly 10,000 civilians have fled battered eastern Aleppo towards government-held districts and the Kurdish-controlled neighborhood of Sheikh Maksoud, a monitoring group said Sunday.

"Nearly 10,000 civilians have fled east Aleppo since the night of Saturday to Sunday," the Syrian Observatory for Human Rights said.

"At least 6,000 of them went to the neighborhood of Sheikh Maksoud, the rest went to government zones of Aleppo."

Government forces retook six rebel-held districts of eastern Aleppo over the weekend, forcing huge numbers of civilians to flee as they pressed their offensive Sunday to retake Syria's second city.

On Sunday, the 13th day of the operation, they took control of the adjacent neighborhoods of Jabal Badra, Baadeeen Inzarat, Al-Sakan, al-Shaabi and Ain al-Tall, according to the Observatory.

Government forces are now "in control of most of the northern part" of Aleppo, according to the monitoring group.

Around 250,000 civilians besieged for months in the east have faced serious food and fuel shortages.

UN envoy Staffan de Mistura warned last week that time was "running out" for efforts to avoid a humanitarian catastrophe in Aleppo.

Once a commercial and industrial hub, Aleppo has seen some of the worst fighting in Syria's nearly six-year war.

Since November 15, regime bombardment of eastern Aleppo has killed 212 civilians, including 27 children, according to the Britain-based Syrian Observatory for Human Rights.

AFP contributed to this report.