Red Cross Warns Evacuation of Aleppo Could Take Days The warring sides will attempt another cease-fire and withdrawal.

 -- The evacuation of thousands of civilians and rebel fighters from the last remaining opposition holdout in eastern Aleppo began today, bused out in convoys arranged by Russia and accompanied by representatives from the International Committee of the Red Cross, marking the city's final surrender to the forces of Syrian President Bashar al-Assad.

As the buses moved out, Assad hailed what he called the complete "liberation" of Aleppo, Syria's second-largest city, much of which has been reduced to ruins by his forces' bombardments over four years of fighting. Although the evacuation is underway, the Red Cross warned that it could take days to complete it.

Twenty buses and at least 10 ambulances crept cautiously into the wrecked streets of the remaining neighborhoods held by rebels in eastern Aleppo around midmorning, after Russian President Vladimir Putin ordered his military to assist in the evacuation of 5,000 fighters and their families as part of a deal allowing the rebels to leave for opposition-held areas outside the city.

Red Cross workers arriving to pick up people described a harrowing situation. "When we arrived, the scene was heart-breaking," Marianne Gasser, the head of the International Committee of the Red Cross in Syria, said in a statement. "People are faced with impossible choices. You see their eyes filled with sadness. It was very moving. No one knows how many people are left in the east, and the evacuation could take days"

Gasser said 3,000 people had been brought out so far in two convoys, which are to carry most of them toward Idlib, a province southwest of Aleppo that is still under opposition control. Ingy Sedky, the Damascus spokeswoman for the International Committee of the Red Cross, told The Associated Press the ambulances were carrying two people at a time and the buses were taking about 50.

About 200 wounded were still stranded in the city, the Red Cross said, saying a third convoy set off as darkness fell.

Russia's Deputy Defense Minister Valery Gerasimov said in a televised statement that Moscow and the Syrian government would guarantee the safety of those leaving and that the Red Cross workers were being accompanied by Russian military officers. The route described by the Russian military takes the convoy through 4 miles of government territory and then through 9 miles outside the city held by rebel groups.

The evacuation was being watched tensely, after a previous attempt fell apart Wednesday, when fighting broke out again, with forces loyal to Assad again pounding the less-than-mile-wide strip of territory where the rebels have been cornered by his forces as they retook the city this week.

There were concerns that Shi'ite militias and Iranian-backed groups, which have provided the backbone of the pro-government forces that retook Aleppo, may not have fully accepted the evacuation deal brokered by Russia, with reports that they fired on rebels as they tried to leave Wednesday. As the first convoy began its route today, workers worried it could come under fire.

"There was firing before we entered east Aleppo for the first evacuation," Gasser said. "Right up until the last minute, it wasn't clear we'd get in. A crane was used to remove some of the debris from the street so the ambulances and buses could get through. There were burned-out cars. Smoke rising from nearby buildings. There was a lot of fear and uncertainty."

But Assad hailed the beginning of the evacuation as marking the end of the battle for Aleppo, declaring the city's "liberation" as making history.

"History is not the same before and after," he said in a video address published online. "I think after liberating Aleppo, we will say that not only the Syrian situation but also the regional and international situation is different.

"This history that is being made now is bigger than the word 'congratulations.’ Everybody is saying congratulations now."

U.S. Secretary of State John Kerry today offered some strong words on Syria and the devastation in Aleppo but mentioned no meaningful policy change on behalf of the United States. He said that he wants to get back to the negotiating table in Geneva and work out a nationwide cease-fire but that Assad is unwilling to live up to agreements.

The Assad regime is carrying out "nothing short of a massacre" and "indiscriminate slaughter," Kerry said. These "are not accidents of war but, frankly, purposeful, a cynical policy of terrorizing civilians."

He added that if Aleppo falls, the war will not end. "We are seeing the unleashing of a sectarian passion," he said.

Aleppo fell to Assad's forces this week after rebel defenses collapsed during a three-week offensive by the Syrian army, significantly bolstered by Shi'ite militias and Iranian troops — an advance that followed months of siege and savage bombing by Russian and Syrian aircraft. At least 50,000 people have fled the rebel-held east in the past month as the government forces advanced, finally abandoning their ruined neighborhoods where they had sheltered for months, low on food and medical supplies while enduring daily airstrikes.

As many as 100,000 people have fled since August, Russia said. Schools, hospitals and other critical infrastructure in rebel areas have been bombed heavily, with hundreds of children killed in recent months.

The victory is the most significant for the Assad regime in years, pushing Syria's five-year civil war into a new phase, with him in a considerably stronger position than before. Until Russia's intervention a year ago, his hold appeared to be flagging, but that situation has now reversed, leaving the opposition to his rule now likely to have to convert into an insurgency, some observers said.

Moscow and Assad have praised the re-establishment of government control over Aleppo as a victory for civilization, but it has come at the cost of flattening neighborhoods held by his opponents.

"In Aleppo, Russia and the Syrian regime seek to make a desert and call it peace," Alex Younger, the head of Britain's MI6 spy agency, said in a public speech last week.

With thousands of people, possibly tens of thousands, still in the rebel zone, there are fears the evacuation deal could still break down. The safe passage of the convoys is being seen as a test of whether Moscow has succeeded in forcing its Iranian and Shi'ite militia allies in the battle to accept the deal, which it brokered with the rebels' ally Turkey.

In the hours before Putin's order, Hezbollah, the Iranian-backed group from Lebanon whose fighters have played a key role in assisting the Syrian army's retaking of Aleppo, questioned in a statement whether the evacuation was possible.

A Turkish official told Reuters that if all goes as planned, the evacuation will take two to three days. Robert Mardini, the International Committee of the Red Cross' Middle East director, called the evacuation just a start and called for access to the rebel area to be kept open, saying there "was so much more to do."

On the day before the evacuation, when shelling was hitting the city again, children trapped in an underground orphanage had pleaded to be allowed to leave.

One 10-year-old girl in a video given to ABC News said, "Please help us get out of Aleppo. All we want is to live like any other child in this world.”

The retaking of Aleppo has been accompanied by reports of atrocities by pro-government forces against some of those fleeing the rebel areas in recent days; the U.N. said it has received reports that 80 people were summarily executed by pro-Assad troops.

Activists on the ground have accused the government of rounding up men as they enter government-held territory. There are fears that many people from areas held by the opposition could now disappear into government torture camps, where tens of thousands of people have been imprisoned by Assad's security forces since protests against his rule began in 2011.

The United States has condemned the violence used in retaking Aleppo, with U.S. Ambassador to the United Nations Samantha Power asking Russian representatives in the U.N. Security Council whether they were "truly incapable of shame."

The United States has sat largely powerless as the city fell to Assad and his allies.

Putin spokesman Dmitry Peskov today told reporters that the U.S. is not involved in the situation unfolding in Aleppo "in any way."