A senior Syrian rebel blamed Iran and its Shia militias for holding up the evacuation of civilians trapped in the eastern rebel-majority area of Aleppo and urged Russia to live up to its commitment to implement the deal.
More than 3,000 people were taken out of east Aleppo on Thursday, but a convoy of about 800 people was turned back the next day and the evacuation suspended. Four evacuaees were also killed, witnesses told Al Jazeera, and people were beaten up and robbed of cash before being sent back.
A new ceasefire deal to evacuate tens of thousands of Syrian opposition fighters and civilians was reached, according to a rebel group official.
However, trapped Syrians waited desperately on Saturday for evacuations to resume and the Red Cross pleaded for a deal to "save thousands of lives".
Munir al-Sayal, head of the political wing of the Ahrar al-Sham rebel group involved in negotiations over the deal, said Iran was insisting people be allowed to leave two rebel-besieged Shia villages in northwest Syria - al-Foua and Kefraya - before letting the Aleppo evacuation happen.
He said Russia was failing to restrain its ally.
"Iran and its sectarian proxies are using the humanitarian situation of our people in besieged Aleppo and preventing civilians from leaving until the evacuation of their groups in al-Foua and Kefraya," Sayal told Reuters news agency in a telephone interview.
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Sayal said Iranian-backed fighters, led by Lebanon's Hezbollah and other Iraqi Shia groups, were behind the detention of hundreds of people trying to leave on Friday.
"These sectarian militias are responsible, but we warn them the safety of our people in Aleppo is the priority and all options are open towards achieving that goal," said Sayal.
He said Moscow's assertion that most civilians had already been evacuated from Aleppo showed Russia was trying to renege on its responsibilities under the deal.
"Russia has failed to restrain the sectarian Shia militias in Aleppo to complete the deal and Moscow should abide by its commitments. There are still civilians in Aleppo who need to be evacuated in harsh weather conditions and Russian statements that besieged Aleppo is empty is absolving itself from following up on the agreement."
Families spent the night in freezing temperatures in al-Amiriyah district, the departure point for evacuations before they were halted on Friday.
"There's no more food or drinking water, and the situation is getting worse by the day," Abu Omar, who waited in the cold for nine hours on Friday, told the AFP news agency. He returned the next day only to be told the buses were not coming.
UN envoy Staffan de Mistura estimated, as of Thursday, about 40,000 civilians and perhaps as many as 5,000 opposition fighters remained in Aleppo's rebel enclave.
In New York, the UN Security Council could vote as early as this weekend on a French-drafted proposal to allow international observers in Aleppo and ensure urgent aid deliveries.
On Friday, US President Barack Obama called for impartial observers to monitor efforts to evacuate civilians, and warned Syrian President Bashar al-Assad would not be able to "slaughter his way to legitimacy".
Aleppo, Syria's second-largest city and once a key cultural and economic hub, has been divided between government forces and rebels since 2012.
The evacuation agreements came a month after the Syrian government and allies launched a military offensive to retake the entire city. Assad has hailed the operation as a victory.
The Syrian conflict started as a largely unarmed uprising against Assad's rule in March 2011. It has since morphed into a full-scale war that has left hundreds of thousands dead and more than half of the country's prewar population displaced inside and outside of Syria.
Source: Al Jazeera and news agencies