More than 3,000 people have been evacuated in buses and ambulances from a besieged rebel-held enclave in the Syrian city of Aleppo, officials say.
The International Committee of the Red Cross (ICRC) says the full evacuation of civilians and rebels is likely to take several days.
Government forces, backed by Russian allies, took nearly all remaining rebel-held parts of Aleppo this week.
It represents a major victory for President Bashar al-Assad.
He hailed the "liberation" of Aleppo and said history was being made.
The evacuation of civilians, rebels and their families had been due to take place on Wednesday but an earlier ceasefire deal collapsed.
"Some 3,000 civilians and more than 40 wounded, including children, were brought out," the head of the ICRC in Syria, Marianne Gasser, said after two convoys left.
"No-one knows how many people are left in the east, and the evacuation could take days," she added.
The evacuees are being transferred to rebel-held areas in neighbouring Idlib province.
US Secretary of State John Kerry meanwhile accused Syrian leaders of carrying out "nothing short of a massacre" in Aleppo and urged them to return to peace talks in Geneva.
"The only remaining question is whether the Syrian regime, with Russia's support, is willing to go to Geneva prepared to negotiate constructively, and whether or not they're willing to stop this slaughter of their own people," he said in Washington.
Analysis by Barbara Plett Usher, BBC News, Washington
John Kerry expressed moral outrage at the fate of Aleppo and he stressed that the Syrian regime was responsible for the failure of a year's worth of US-Russian negotiations aimed at a nationwide ceasefire and peace talks.
But he didn't offer any new plan to end the conflict. Nor did he accept that the fall of Aleppo was also due to a failure of US diplomatic strategy. "You can't make someone do something through diplomacy that they're not prepared to negotiate," he told me.
Critics in Washington, though, have slammed the Obama administration for refusing to back that diplomacy with the threat of credible force, giving Mr Kerry very little to work with other than good faith.
Some have faulted the secretary of state for having too much faith in Russia's willingness for a deal - "delusional diplomacy", the Washington Post called it.
Mr Kerry made clear he would continue his tireless efforts to reach a peace deal. But the fall of Aleppo almost certainly means he has run out of time to do so in the waning weeks of this administration, and the Syria crisis will be passed on to the next one.
Syrian state media said rebels had blown up their ammunition dumps and destroyed documents before leaving the city.
A statement from the Russian Centre for the Reconciliation of Opposing Sides in Syria, part of Russia's ministry of defence, said the Syrian authorities had guaranteed the safety of all members of the armed groups who decided to leave Aleppo.
The rebels confirmed a fresh ceasefire had come into effect at 03:00 GMT and that a new deal had been agreed.
As operations began, an ambulance service official in eastern Aleppo said that one convoy of ambulances had been shot at, with three people injured.
The White Helmets civil defence group tweeted that one senior volunteer had been shot and injured by a sniper while clearing an evacuation route for ambulances.
Where are the evacuees being taken?
Buses and ambulances are taking the injured, civilians and rebel fighters to the neighbouring province of Idlib, most of which is controlled by a powerful rebel alliance that includes the jihadist group Jabhat Fateh al-Sham.
The buses left Aleppo via the road through the government-controlled south-western district of Ramousseh, heading towards the nearby rebel-held towns of Khan Touman and Khan al-Asal.
The chief of the Russian military's General Staff, Gen Valery Gerasimov, told a news briefing: "A humanitarian corridor has been created for the evacuation of militants."
"This corridor is 21km long," he said, adding, "6km lie across Aleppo's territories controlled by government troops and another 15km through territories in the hands of illegal armed groups."
Turkey, which helped to broker the evacuation, is preparing to receive some of the most vulnerable civilians, President Recep Tayyip Erdogan said.
In a televised address, he said Turkey would take "children, elders, those who are really in difficult conditions".
The head of the Turkish Red Crescent, Kerem Kinik, told reporters that the wounded would be the first to be transferred.
How many remain in eastern Aleppo?
UN Syria envoy Staffan de Mistura said about 50,000 people were still trapped and he warned that moving those evacuated to Idlib might not prove much safer.
"If there is no political agreement and a ceasefire, Idlib will become the next Aleppo," he told reporters in Paris.
The 50,000 are said to include about 4,000 fighters and about 10,000 of their family members.
Aleppo's besieged residents have faced weeks of bombardment and chronic food and fuel shortages.
Russian Lt Gen Viktor Poznikhir said on Thursday that, with the evacuation, the Syrian armed forces had almost finished their operations in Aleppo. Fighting has raged there for four years.
What will the government do next?
In October, President Assad said victory in Aleppo would be "the springboard... to liberate other areas from terrorists", a term the government uses to describe all rebel fighters.
He singled out Idlib province, west of Aleppo, that is almost entirely controlled by an alliance of Islamist rebel factions and Jabhat Fateh al-Sham, formerly known as al-Nusra Front.
Idlib contains border crossings used by rebels to receive supplies from Turkey, a key backer. It also borders the coastal province of Latakia, the heartland of Mr Assad's minority Alawite sect.