Efforts to evacuate the last rebel-held areas of Syria's Aleppo were underway on Thursday, with opposition fighters and civilians preparing to leave the city after years of fighting.
The rebel withdrawal will pave the way for President Bashar al-Assad's forces to reclaim complete control of Syria's second city, handing the regime its biggest victory in more than five years of civil war.
More than a dozen empty buses and several ambulances moved towards a staging area in the south of the city where evacuees were expected to arrive and board the vehicles, an AFP correspondent said.
"People are getting on the buses at the staging ground. The operation is proceeding as planned. Everything is fine, people are gathering," said Ingy Sedky, a spokeswoman in Syria for the International Committee of the Red Cross, which is assisting in the operation.
"We expect this operation to take some time, because there will be multiple rotations. No one has left the staging ground yet," she told AFP.
It was unclear how many people would be involved in the first evacuation or how long the whole process could take.
Syrian state television reported that at least 4,000 rebels and their families would be evacuated under the plan.
A first evacuation expected to take place 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 that Syrian authorities had guaranteed the safety of the rebels leaving the city and confirmed preparations were underway.
It said the rebels would be evacuated towards the northwestern Syrian city of Idlib, a major opposition stronghold.
- Ambulance 'fired on' -
The Russian military said it was monitoring the operation with surveillance cameras and drones.
The ICRC said it had sent 10 ambulances and about 100 volunteers and staff from the Red Crescent to assist.
Rebel officials said the evacuees would leave via the district of Al-Amiriyah, and then cross through the government-controlled area of Ramoussa on the southern outskirts of the city.
Earlier, Ahmad al-Dbis, who heads a unit of doctors and other volunteers that are coordinating the evacuation of wounded people, said injured civilians and their families were already gathering at Al-Amiriyah.
Dbis said there were reports that regime forces had fired on an ambulance transporting the injured to Al-Amiriyah, wounding three people including a member of the White Helmets civil defence organisation.
One of the wounded was initially reported to have died, he said, but later an AFP correspondent said the situation was unclear.
On Wednesday, cold and hungry civilians had gathered for the initial planned evacuation but were instead sent running through the streets searching for shelter as the fighting resumed.
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Russia accused the rebels of having violated the ceasefire while Turkey accused Assad's regime and its supporters of blocking the evacuation.
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.
A source close to the regime with knowledge of the negotiations said the revived agreement now also involved the evacuation of sick and wounded residents of the two villages.
- A month into offensive -
The new deal Thursday was announced a month to the day after pro-government forces launched a major new offensive to retake all of Aleppo, large parts of which had been in rebel hands since 2012.
Backed by foreign militia forces including fighters from Lebanon's Shiite Hezbollah movement, the advance made rapid gains, seizing more than 90 percent of rebel territory within a few weeks.
More than 465 civilians, including 62 children, have died in east Aleppo during the assault, according to the Syrian Observatory for Human Rights.
Another 149 civilians, among them 45 children, have been killed by rebel rocket fire on government-held zones in the same period, the Britain-based monitoring group said.
The United Nations and Western countries this week condemned alleged atrocities being carried out by pro-government fighters during the advance, including reported summary executions of men, women and children.
A UN panel said on Wednesday that it had also received reports that rebel fighters were blocking civilians from leaving and using them as human shields.
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 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.
- Shrinking rebel territory -
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.
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.
"We are striving to secure a ceasefire throughout the country and for negotiations for a political solution to start," Foreign Minister Mevlut Cavusoglu said.