Brokered by regime ally Russia and opposition supporter Turkey, the evacuation plan has moved forward in fits and starts
An AFP correspondent in the government-held neighbourhood of Ramussa -- through which thousands of evacuees have passed in recent days -- saw no convoys leaving the last pocket of opposition-controlled Aleppo on Wednesday morning.
Heavy snow was blanketing the city and swirling through crumbled buildings, adding to the misery of thousands still inside the last pocket of what was once a crucial stronghold of Syrian rebel forces.
Workers in the red uniforms of the Syrian Red Crescent, which has been helping with the evacuations, huddled by the side of the road, their white ambulances parked nearby barely visible in the snow.
At least 25,000 people have left rebel districts of Aleppo since opposition fighters agreed last week to withdraw from the city after years of fighting, according to the International Committee of the Red Cross, which is overseeing the operation.
The retreat from Aleppo -- which had been divided into a rebel-held east and government-controlled west since 2012 -- marks the biggest victory for President Bashar al-Assad's forces in nearly six years of civil war.
It follows a month-long army offensive and weeks of siege that killed hundreds and left rebels with less than 10 percent of the territory they once controlled in the city.
Brokered by regime ally Russia and opposition supporter Turkey, the evacuation plan has moved forward in fits and starts but appeared to be reaching its end.
On Tuesday soldiers used loudspeakers to warn remaining fighters and civilians it was time to leave eastern districts.
A military source told AFP the army was expected to enter the rebel enclave "to clean the area after the fighters leave".
Ahmad al-Dbis, who heads a team of doctors and volunteers coordinating evacuations, said around 150 people had been able to leave at dawn on Wednesday in two buses and three ambulances.
But more were still waiting, with a convoy of 31 buses and about 100 other vehicles being prepared in rebel territory, Dbis said.
It was unclear how many civilians remained inside east Aleppo, though Dbis said there were "a few thousand" who were still hoping to leave.
As part of the evacuation deal, some residents were being evacuated in parallel from Fuaa and Kafraya, two Shiite-majority villages in northwestern Syria besieged by rebels, who are mainly Sunni Muslims.
Shiite-dominated Iran -- another key Assad ally -- was reported to have insisted on the evacuations of Fuaa and Kafraya for the Aleppo withdrawal to go ahead.
About 750 people have so far been able to depart from the villages, according to the ICRC.
A Syrian military source told AFP that delays in evacuations from Aleppo were "procedural" and connected with the need to "synchronise" operations in the two villages.
"More than 1,700 people are waiting to leave Fuaa and Kafraya," the source said.
The evacuation of Aleppo's rebel sector is seen as a pivotal moment in a war that has killed more than 310,000 people and triggered a major humanitarian and refugee crisis.
As well as handing a major victory to Assad, it has given fresh energy to international efforts to end the conflict.
Russia, Iran and Turkey agreed on Tuesday to guarantee Syria peace talks and backed expanding a ceasefire in the country, laying down their claim as the main powerbrokers in the conflict.
In a joint statement, Russian Foreign Minister Sergei Lavrov said the Aleppo evacuation should finish within "one or two days".
Repeated diplomatic attempts -- including several rounds of peace talks in Geneva -- have failed to resolve Syria's conflict, but UN envoy Staffan de Mistura has said he hopes to convene new negotiations in Geneva in February.
The United States, another supporter of the opposition, has for years been a key player in the diplomatic efforts but has been largely excluded from involvement in the evacuation effort.
With President Barack Obama in his final weeks in office, Lavrov on Tuesday praised the Turkey-Iran-Russia format on Syria as the "most effective" way forward.
In a rare show of international unity, the UN Security Council did on Monday unanimously adopt a French-drafted resolution to monitor the Aleppo evacuations.
The government and other parties on the ground agreed to allow 20 observers to be sent to east Aleppo to monitor evacuations, UN spokesman Stephane Dujarric said, but it was unclear when they would be able to deploy.