Around 50,000 people, the majority civilians, were still trapped in eastern Aleppo even as an evacuation deal was under way, the UN peace envoy for Syria and French foreign minister said on Thursday.
"There are 50,000 people, including 40,000 civilians unfortunate enough to live in that part of the city. The rest are fighters, numbering between 1,500 and 5,000, and their families," the UN's Staffan de Mistura told reporters in Paris, alongside France's Jean-Marc Ayrault.
Turkey had earlier said 80,000 to 100,000 civilians were likely still trapped in eastern Aleppo.
"Our priority is for our UN colleagues to be present with the people (who have been evacuated) and that the fighters be respected under the terms of this deal," De Mistura said.
Under the terms of the evacuation agreement negotiated by regime backer Russia and rebel supporter Turkey, the people currently being evacuated from eastern Aleppo will be taken to the northwestern province of Idlib, an opposition bastion.
"We don't know what will happen in Idlib. If there is no political agreement and a ceasefire, Idlib will become the next Aleppo," De Mistura said.
Ayrault meanwhile repeated France's call for "the deployment, as quickly as possible, of UN observers, of all UN personnel who are already on the ground, and who can be deployed in the coming hours."
A UN Security Council meeting requested by France, and which is expected to take place on Friday, "will specifically examine the deployment of observers in order to ensure there are no abuses, no acts of revenge, and that the civilian population is protected".
He added: "This can be done extremely quickly."
Ayrault meanwhile urged "a ceasefire for the whole country and for a return to negotiations".
Hundreds of people evacuated from eastern Aleppo
Thousands of civilians and rebels left Aleppo on Thursday under an evacuation deal that will allow Syria's regime to take full control of the city after years of fighting.
The rebel withdrawal began a month to the day after President Bashar al-Assad's forces launched a new offensive to recapture Aleppo and will hand the regime its biggest victory in more than five years of civil war.
But Marianne Gasser, the head of the International Committee of the Red Cross (ICRC) in Syria, warned it could take days to complete the evacuation operation in the Syrian city of Aleppo.
In a statement, she said about 3,000 civilians and more than 40 wounded, including children, were brought out in the first two evacuations. Darkness had already set in when the third convoy set off to evacuate more people.
In a video message to Syrians, Assad said the "liberation" of Aleppo was "history in the making".
A revived agreement on a ceasefire and the evacuations was announced on Thursday, after an initial plan for civilians and fighters to leave rebel-held parts of the city collapsed the previous day amid renewed clashes.
The evacuation began with a convoy of ambulances and buses crossing into a government-held district in southern Aleppo around 2:30 pm (1230 GMT).
A Syrian military source told AFP that 951 evacuees, including 108 wounded, were in the convoy. Most were civilians but about 200 rebel fighters were among them, the source said.
The vehicles arrived just over an hour later in opposition territory about five kilometres (three miles) west of the city, and they followed by a second convoy of 15 buses, state media and a doctor at the scene said.
"The wounded will be transferred to... nearby hospitals for treatment," said Ahmad al-Dbis, who heads a unit of doctors and other volunteers coordinating the evacuation of wounded people.
State television earlier showed images of the convoys' blinking lights moving through the government-held Ramussa neighbourhood.
EU to use all diplomatic channels to press for aid to Aleppo
The European Union will use all diplomatic channels to press for humanitarian aid to reach Aleppo and for civilians to be evacuated from the Syrian city, the chairman of EU leaders Donald Tusk said on Thursday.
Tusk said it was not possible to stop the conflict in Syria by force and that EU leaders realised they were not effective enough in dealing with it. He said EU leaders, who met for talks in Brussels, were more radical in their views on the Syrian conflict that three months earlier, but had not decided to impose new sanctions on Russia for its role in the conflict.
Residents gather near a green government bus for evacuating from eastern Aleppo, Syria, Thursday, Dec. 15, 2016 (AAP) Source: AAP
Kerry says Assad government carrying out 'massacre' in Aleppo
US Secretary of State John Kerry said on Thursday that the government of Syrian President Bashar al-Assad is carrying out "nothing short of a massacre" in Aleppo.
Kerry, speaking at a news briefing, said the United States was seeking an immediate, verifiable, and durable cessation of hostilities in Aleppo, and he called on the international community to exert pressure to move the process forward.
'We will return'
The evacuees spent hours gathering earlier at a staging area in Aleppo's southern Al-Amiriyah district.
An AFP correspondent there saw people piling onto the green buses, filling seats and even sitting on the floor, with some worried there would not be another chance to evacuate.
Many were in tears and some hesitated to board, afraid they would end up in the hands of regime forces.
On the dusty window of one of the buses someone had written "One day we will return".
Related reading
Syria crisis: How you can help those in need
Each bus carried a member of the Syrian Red Crescent wearing the organisation's red uniform, riding at the front next to the driver.
Ingy Sedky, the International Committee of the Red Cross's spokeswoman in Syria, said the first convoy included 13 ambulances and 20 buses carrying civilians.
State television reported that at least 4,000 rebels and their families would be evacuated.
A first evacuation attempt on Wednesday morning fell apart, with artillery exchanges and resumed air strikes rocking the city until the early hours of Thursday.
But the agreement, brokered by Syrian regime ally Moscow and opposition supporter Ankara, was revived following fresh talks.
The defence ministry in Moscow said Syrian authorities had guaranteed the safety of the rebels leaving the city.
The head of the UN-backed humanitarian taskforce for Syria, Jan Egeland, told reporters in Geneva that most of those evacuated from Aleppo would head to opposition stronghold Idlib, in Syria's northwest.
France on Thursday requested urgent closed-door consultations at the UN Security Council on the evacuation of civilians and plans for aid deliveries to Aleppo, with Paris's envoy calling for international observers to monitor operations.
Related reading
Aleppo assault likely a war crime: UN
Ambulance 'fired on'
The evacuation was going ahead despite reports earlier Thursday of pro-regime forces firing on an ambulance transporting the injured to Al-Amiriyah, wounding three people including a member of the White Helmets civil defence organisation.
On Wednesday, cold and hungry civilians had gathered for the initial planned evacuation but were instead sent running through the streets searching for cover as fighting resumed.
Russia accused the rebels of having violated the ceasefire while Turkey accused Assad's regime and its supporters of blocking the evacuation.
WATCH: What's next for Aleppo?
Iran, another key Assad backer, was reported to have imposed new conditions on the agreement, including the evacuation of some civilians from two Shiite-majority villages in northwestern Syria under rebel siege.
On Thursday, nearly 30 vehicles were headed to Fuaa and Kafraya to evacuate sick and wounded residents, the governor of neighbouring Hama province, Mohamed al-Hazouri, told state news agency SANA.
A Syrian source on the ground told AFP that "1,200 injured and sick people and their families will be evacuated."
Backed by foreign militia forces including fighters from Lebanon's Shiite Hezbollah movement, the advance launched last month made rapid gains, leaving the rebels cornered in a tiny pocket of the territory they had controlled since 2012.
More than 465 civilians died in east Aleppo during the assault and another 149 were killed by rebel rocket fire on government-held areas, according to the Syrian Observatory for Human Rights monitoring group.
Shrinking rebel territory
More than 310,000 people have been killed since the Syrian conflict began, and over half the population has been displaced, with millions becoming refugees.
The United States and other Western nations, Turkey, and Gulf Arab states all backed opposition forces during the war but their support was limited.
The conflict, which began in 2011 with anti-government protests that were brutally put down, saw a turning point last year when Russia launched an air war in support of Assad.
With Aleppo out of rebel hands, the largest remaining rebel bastion is Idlib province, which is controlled by an alliance dominated by former Al-Qaeda affiliate Fateh al-Sham Front.
British Foreign Secretary Boris Johnson on Thursday summoned the Russian and Iranian ambassadors to convey what he said on Twitter was his "profound disquiet" over the violence in Aleppo.
Diplomatic efforts -- including several rounds of peace talks in Geneva -- failed to make headway in resolving the conflict.
After upping its involvement by brokering the Aleppo deal, Turkey said it would meet with Russia and Iran in Moscow on December 27 to discuss a political solution to the entire conflict.
The United States and other Western nations, Turkey, and Gulf Arab states all backed opposition forces during the war but their support was limited.
The conflict, which began with anti-government protests that were brutally put down, saw a turning point last year when Russia launched an air war in support of Assad.
With Aleppo out of rebel hands, the largest remaining rebel bastion is Idlib province, which is controlled by an alliance dominated by former Al-Qaeda affiliate Fateh al-Sham Front.
Rebels also hold territory in southern Daraa province and the Ghouta region around Damascus, although the army has been advancing there.
