BEIRUT -- Some 50,000 civilians have fled eastern Aleppo over the past two days in a "constant stream," Russia said Saturday, as Syrian government forces close in on the last pocket of opposition control in the northern city.

Russian Defence Ministry spokesman Maj. Gen. Igor Konashenkov said that Syrian troops have suspended their offensive to allow for the evacuation of civilians, but the activist-run Syrian Observatory for Human Rights says heavy clashes are still underway.

Konashenkov said that on Saturday alone more than 20,000 civilians left rebel-controlled Aleppo districts through humanitarian corridors. The military is live streaming images from drones showing the exit.

Backed by Russia and other allies, Syrian President Bashar Assad's forces have driven the rebels from nearly all of eastern Aleppo, which was captured by the opposition in 2012.

"People are moving in a constant stream through humanitarian corridors into the government-controlled districts," Konashenkov said at a briefing. "After civilians exit, the Syrian army will continue its operation to free Aleppo neighbourhoods, and the militants will be either pushed out or destroyed."

Konashenkov said the Russian military is providing civilians who have left eastern Aleppo with temporary accommodation, hot meals and medical assistance. He also urged the U.S., Britain, the European Union, Canada and international organizations to provide humanitarian assistance to them.

The U.N. human rights office has expressed concern about reports that hundreds of men have vanished after crossing from eastern Aleppo into government-controlled areas.

U.S. Secretary of State John Kerry and European and Arab diplomats are meeting members of Syria's opposition in Paris on Saturday. Kerry said he is working to ensure their safety and to save Aleppo "from being absolutely, completely destroyed."

U.S. and Russian military experts and diplomats are meeting in Geneva on Saturday to work out details of the rebels' exit from eastern Aleppo.

The Russian military's Center for Reconciliation in Syria said Russian sappers have continued defusing mines in the city, clearing 8 hectares (about 20 acres) since Friday.