The evacuation of civilians and opposition fighters from eastern Aleppo was suspended yesterday after rebels opened fire on a convoy at one of the crossing points of the rebel-held enclave, according to Syrian state TV.
It was not immediately clear how long the suspension, which was announced within a couple of hours after the evacuations resumed on Friday, would last.
Ikhbariya TV also claimed that the rebels tried to take with them captives they had seized and were holding in the rebel enclave.
Lebanon's Al-Manar Hezbollah TV said the Syrian army stopped the process because the rebels had violated the ceasefire deal. Hezbollah militiamen are fighting in the Syrian civil war alongside President Bashar Assad's forces.
Lebanon-based Al-Mayadeen TV said buses which were parked at the Ramouseh crossing point in southern Aleppo had left the area after it was targeted by gunmen.
Earlier, Syrian state TV reported that four convoys of fighters and civilians had departed from the rebel enclave on Friday.
In the central province of Hama, buses and ambulances were waiting to evacuate thousands of people from two Shiite villages besieged by rebels, a last-minute condition which became part of the ceasefire deal for Aleppo.
Iran had demanded that the evacuations from Foua and Kefraya be tied in with the mass movement out of eastern Aleppo.
Meanwhile, Russian President Vladimir Putin said he and his Turkish counterpart are working to launch a new round of peace talks between the Syrian government and the opposition - negotiations which would take place in Kazakhstan's capital, Astana.
Mr Putin, speaking during on a visit to Japan on Friday, said Ankara had helped to broker the rebel exit from Aleppo that is currently under way. He said he and Turkish President Recep Tayyip Erdogan are also working for an overall truce in Syria.
The Russian leader said that once the Syrian army secures control of all of Aleppo, civilians will be able to return to their homes.
It was not immediately clear if western-backed Syrian opposition would accept such a location for peace talks with President Bashar Assad's government.
A Turkish official said his country's aid organisations are helping Syrians who have been evacuated from Aleppo to a border area held by the opposition in Syria's Idlib province.
Deputy Prime Minister Veysi Kaynak said on Friday that "20 buses from Aleppo have reached the safe zone under control of the Free Syrian Army in Idlib". He said 30-35 injured people were being treated at the Sahra hospital just over the border.
Mr Kaynak said there had been a discussion with Syrian opposition forces over the possibility of establishing a centre "within a security zone in Syria". He told the private Dogan news agency that "Idlib has no physical capacity to accommodate so many people".
He estimated there are 80,000 to 100,000 individuals who would like to leave Aleppo under the ceasefire deal which Turkey helped broker.
He added that Turkey is willing to provide assistance to "legitimate" Syrian opposition groups to help meet their needs. The minister spoke after visiting the Cilvegozu border crossing with Syria in southern Turkey.
Russia said that all women and children have been taken out of eastern Aleppo and that a final sweep by the Syrian military is under way to clear out the last remaining rebels in the city.
A statement on Friday from the Russian military's Centre for Reconciliation in Syria said the evacuations have been "completed".
It came shortly after the Syrian government said it was suspending the evacuations because a convoy leaving Aleppo was fired on by the rebels.
The UN and international aid agencies insist there are still people in eastern Aleppo waiting to be evacuated.
Russia said that more than 9,500 people, including more than 4,500 rebels and 337 wounded, have been taken out of the rebel-held districts in eastern Aleppo.
The Russian military also says some die-hard militants have stayed behind and are firing on the Syrian government troops.
The UN health agency's top official in Syria says negotiations are under way in hopes of resuming evacuations from rebel-held parts of eastern Aleppo.
Elizabeth Hoff, the Syria representative for the World Health Organisation, says that the agency knows "there are a large number of women and children, and there are others, who are still inside and want to get out".
She spoke by phone from government-controlled western Aleppo, after Russia's military claimed that all women and children had been taken out of eastern Aleppo during evacuations that began a day earlier involving WHO help.
Ms Hoff says that "negotiations are ongoing" through the office of the UN envoy for Syria to try to restart the evacuations.
She says has no indication that the evacuations have been completed.
