Thousands of civilians are trapped in increasingly desperate conditions in Aleppo, Syria as disagreements over an evacuation plan caused delays.
Reporters described seeing people sleeping in the streets in freezing conditions with little or no food.
The delays appeared to be caused by an argument over moving civilians from two government-controlled areas in Idlib.
But Syrian state TV reports said buses entered eastern Aleppo around noon local time to begin evacuations.
A plan to evacuate Eastern Aleppo collapsed on Friday, leaving civilians stranded at various points along the route out without access to food or shelter.
UK-based monitoring group the Syrian Observatory for Human Rights said on Sunday that a rebel group formerly known as the Nusra Front was preventing buses entering the besieged villages of two government-held areas - Foah and Kefraya in Idlib province.
Pro-government forces had reportedly demanded that a group of people needing medical treatment also be allowed to leave the two areas.
Reports said a new agreement was reached in the early hours of Sunday but delays meant thousands of civilians continued to be stranded throughout the morning.
The International Red Cross said it was preparing for the rescue efforts to resume. Mounir Hakimi, the chair of Syrian Relief, told the BBC on Sunday that the charity was waiting on the Syria-Turkey border to receive civilians.
"We're waiting for the agreement to re-establish again," he said. "The news I have this morning is that an agreement has been reached six hours ago and the team is getting ready."
UN vote
France has proposed that UN officials should monitor evacuation efforts and report on the protection of civilians and the UN will vote on Sunday on whether to send observers to the stricken city.
There are concerns that the UN motion on observers may be resisted by Russia, an ally of Syria's president and a veto-wielding Security Council member.
Moscow has vetoed six resolutions on Syria since the conflict began in 2011.
France circulated a draft text late on Friday stating that the council is "alarmed" by the worsening humanitarian crisis in Aleppo, where "tens of thousands" are in peril.
At least 6,000 people left east Aleppo under a fragile truce on Thursday but the operation was halted a day later.
The besieged city has seen rapid government advances in recent weeks.