Updated at 7:15 p.m. ET
Evacuations of east Aleppo have resumed, after a series of false starts and broken cease-fires.
And United Nations officials said more than 100 U.N. humanitarian staffers are in place and could begin monitoring the evacuation under terms of a U.N. resolution approved unanimously Monday.
Video posted by activists shows evacuees arriving at rebel-held countryside by night, NPR's Alison Meuse reports. The BBC says about 1,000 people have made it out from the war-torn city in the latest evacuation push.
UNICEF says that 47 children who were trapped at an orphanage in east Aleppo have been evacuated, "with some in critical condition from injuries and dehydration," UNICEF Regional Director Geert Cappelaere said in a statement.
Last week, a video from the orphanage had been posted on the Internet, with one of the children saying, "We want to live like everyone else."
Cold weather in Aleppo, where it's been well below freezing overnight, has compounded the suffering of those waiting to be moved.
The aid group Mercy Corps, which has been working in and around Syria, said Monday morning that the organization and its partner groups have helped more than 1,000 evacuees from Aleppo.
"The people we are welcoming have been through hell — the level of trauma they have experienced is impossible to describe or comprehend," Casey Harrity, director of programs at Mercy Corps, said in a statement.
Over the past week, the shrinking rebel-held enclave in Aleppo has seen multiple cease-fires and evacuation attempts as the city's rebel forces are essentially surrendering to backers of Syrian President Bashar Assad.
One cease-fire collapsed before negotiations could begin. A second cease-fire and evacuation effort lasted just one day. Buses were set to begin running again on Sunday, but that effort, too, ended before it began.
Negotiation attempts are complicated by the many-sided nature of the conflict in Syria. Many of the deals failed because of disputes over the Shiite villages of Foua and Kefraya, which are under siege by Sunni rebel groups. Some Shiite allies of the Assad regime have demanded that those cities be aided or evacuated as part of any truce or evacuation in Aleppo; some rebel factions have apparently refused to honor agreements on that point.
The planned evacuations on Sunday were halted after media reports that several buses headed to Foua and Kefraya were set on fire, as NPR reported Sunday.
"The rebel attack prompted pleas from eastern Aleppo to allow the reciprocal deal to go through," Alison reports from Beirut.
Now U.N. aid official Jan Egeland says evacuations have resumed in those villages as well, although "thousands remain trapped on both sides," Alison says.
The U.N. Security Council approved a compromise French-Russian resolution urging the immediate deployment of U.N. monitors to watch over the evacuation and "the well-being of civilians" remaining in the city, The Associated Press reported.
Francois Delattre, France's U.N. ambassador, said the resolution aims "to avoid new mass atrocities by the forces on the ground and the militias in particular."