A "humanitarian pause" announced by Russia has come into effect in Aleppo to allow civilians and rebel fighters who want to leave the northern Syrian city.
The pause formally started at 8 a.m. local time (0500 GMT/UTC) on October 20.
Moscow said the originally proposed eight-hour pause would be extended by three hours until 7 p.m., and suggested it could prolong the measure further.
Russia earlier said strikes by Syrian and Russian warplanes had been halted on October 18.
The Syrian military said it was opening exit corridors to provide safe passage for those leaving.
But clashes between rebels and government forces erupted on the front line in the divided city, with both sides putting the blame on one another.
Syrian government forces, backed by Russia, launched last month an offensive on Aleppo's rebel-held areas.
"What is happening in Aleppo is a war crime,” French President Francois Hollande said after talks with the German and Russian leaders in Berlin.
German Chancellor Angela Merkel condemned the bombardment of Syria's largest city as "inhumane."
Russia has rejected the accusations, with President Vladimir Putin describing them as "rhetoric" that do not take into account the realities in Syria.