The evacuation of civilians and rebel fighters from remaining rebel-held territory in the Syrian city of Aleppo was suspended on December 16 amid conflicting allegations of cease-fire violations.
The Syrian government said it was suspending the evacuations because a convoy leaving Aleppo was fired on by the rebels.
However, a rebel official and pro-opposition Orient TV claimed that pro-government Shi'ite militias fired on bus convoys leaving Aleppo, the Reuters news agency reported.
Reuters quoted an unnamed Syrian government official overseeing the evacuation as saying: "The operation is not yet complete. There are many who should have left. But the operation halted before its end."
It was not immediately clear how long the suspension would last. It was announced several hours after the evacuations resumed for a second day on the morning of December 16.
Earlier in the day, Syrian state TV was reporting that four convoys with fighters and civilians had departed from the rebel enclave in eastern Aleppo.
Meanwhile, the Russian military said that the evacuations have been “completed.” It claimed that all women and children have been taken out of eastern Aleppo.
The statement from what the Russian Defense Ministry calls its Center for Reconciliation in Syria said that government forces are carrying out a final sweep to clear out the last remaining rebels in the city -- although the Associated Press reported that there was no evidence of this on the ground.
The Russian statement said that some die-hard militants have stayed behind and are firing on Syrian government forces.
The World Health Organization (WHO) said the evacuation of civilians and wounded people had been halted and aid agencies and vehicles ordered to leave the area without explanation.
"The ICRC (International Committee of the Red Cross) and SARC (Syrian Arab Red Crescent) and WHO [were] informed to leave the area with ambulances and buses, no reason was given," WHO representative Elizabeth Hoff, speaking from western Aleppo, told a news briefing in Geneva.
"I assume the message came from the Russians who are monitoring the area," she said. "The worrying part of this is there are still in besieged enclaves of Aleppo high numbers of women and infants, children under 5 that need to get out."
'Nothing Short Of A Massacre'
Earlier, Syrian state TV was reporting that the evacuations continued for the second day, saying four convoys with fighters and civilians departed from the rebel enclave in eastern Aleppo December 16.
The evacuation was being conducted under a cease-fire deal brokered by Russia and Turkey after Syrian President Bashar al-Assad's forces and their allies drove rebels out of most of eastern Aleppo in an offensive that has been sharply criticized by the UN and Western governments.
U.S. Secretary of State John Kerry accused Assad of committing "nothing short of a massacre" in Aleppo.
"We are convinced that the killing and suffering in Syria could stop, and it could stop very, very quickly if Russia and the [Syrian] regime made the decision to do so,” Kerry said on December 15.
UN Secretary-General Ban Ki-moon, speaking to reporters in New York on December 16, strongly condemned international inaction to stop the suffering in Aleppo.
"The carnage in Syria remains a gaping hole in the global conscience. Aleppo is now a synonym for hell," Ban said. "As I told the [UN] Security Council three days ago, we have collectively failed the people of Syria. Peace will only prevail when it is accompanied by compassion, justice, and accountability for the abominable crimes we have seen."
Four Syrian organizations accused Russia, a key ally of Assad in the more than five-year-old civil war, of involvement in war crimes in Syria.
In a letter to a UN inquiry on Syria, the group said that Russian air strikes in the Aleppo area have killed some 1,207 civilians, 380 of them children.
"Evidence clearly indicates that Russia has committed or been complicit in war crimes in Syria," says the letter, which listed 304 alleged attacks carried out in Aleppo primarily between July and December.
The letter was signed by the Syrian Civil Defense search-and-rescue group, also known as the White Helmets, the Syrian Network for Human Rights, the Independent Doctors Association, and the Violations Documentation Center.
Russia has said it stopped conducting air strikes in Aleppo in mid-October.
Rebels had controlled the eastern part of Aleppo, Syria's biggest city before the civil war, since 2012, and the capture of most of the city is a major victory for Assad.
Russian President Vladimir Putin said on December 16 that "the next step" would be "to reach agreement on a complete cease-fire across all of Syria."
Speaking during a visit to Japan, Putin said that he and Turkish President Recep Tayyip Erdogan were working to launch a new round of peace negotiations between the Syrian government and the opposition.
Putin said the proposed talks could take place in Astana, the capital of Kazakhstan.
Putin didn’t mention any involvement of the United States or the United Nations in the new round of Syria peace talks.
However, he played down the idea that the proposed Astana talks would sideline or overshadow similar talks brokered by the United Nations that have been held intermittently in Geneva.
"It won't compete with the Geneva talks, but will complement them," Putin said.
Putin’s remarks come a day after UN envoy for Syria Staffan de Mistura said the United Nations would have to broker any Syria talks for them to have legitimacy.
Russia has given Assad crucial military and diplomatic backing throughout the conflict, which began with a forceful government crackdown on pro-democracy protesters in 2011 and erupted into a civil war that has killed more than 250,000 people.
Moscow helped turn the tide in the government's favor with a major campaign of air strikes that began in September 2015 and that Western governments say has mainly targeted rebels rather than Islamic State militants.
The United States is leading a coalition targeting IS militants who sezied large parts of northern Iraq and Syria in 2014.