Thousands of trapped civilians and rebels are waiting to leave east Aleppo in Syria after a new deal was reportedly reached for evacuations to resume.
Government and rebel sources say the agreement will allow people to leave several besieged enclaves in Syria.
But hours after the announcement, aid agencies were still waiting for the operation to start.
As well as east Aleppo, the deal is also said to include the evacuation of two other rebel-held towns and two towns loyal to the government.
At least 6000 people left east Aleppo under a fragile truce on Thursday, but evacuations were stopped on Friday after pro-government militias demanded that wounded people also be brought out of al-Foua and Kefraya, and protesters blocked the road out of Aleppo.
Confusion reigned on Friday morning when the evacuation, which was taking place along corridors out of Aleppo towards rebel-held areas (Khan al-Asal and Khan Touman), was stopped.
The government said rebel fighters had fired on the convoys at a checkpoint at Ramousseh. Rebels said pro-government forces opened fire.
Munir al Sayal, the head of the political wing of the Ahrar al Sham rebel group involved in negotiations over the deal, said it was Iran insisting that people be allowed to leave al-Foua and Kefyra before allowing the Aleppo evacuation to resume. 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 Kefyra," Mr Sayal told Reuters in a telephone interview.
Mr Sayal also said Iranian-backed Shi'ite fighters led by Lebanon's powerful Hezbollah militia and Iraqi Shi'ite groups were behind the detention of hundreds of people trying to leave on Friday, leading to some deaths before they were turned back in efforts to disrupt the evacuation.
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.
The agreement to evacuate the civilians and fighters was reached mainly between Russia, whose aerial bombing of Aleppo played a critical role in the defeat of the insurgents, and Turkey, which backs the mainstream rebels, acting as a go-between for the main insurgent groups.
"Russia has failed to restrain the sectarian Shi'ite militias in Aleppo to complete the deal and Moscow should abide by its commitments," Mr Sayal said.
"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."
The United Nations Security Council is expected to vote over the weekend on a French-drafted proposal to ensure the operation is co-ordinated by international observers, with humanitarian aid allowed into Aleppo and hospitals given protection.
Correspondents said thousands of cold and hungry civilians remain stranded in the rebel-held east of the city, waiting to be moved to safety.
The International Committee of the Red Cross (ICRC) called on all sides to provide guarantees and allow the evacuation to be completed.
"It's important that the parties on the ground do their utmost to end this limbo," ICRC Syria head Marianne Gasser said.
"People have suffered a lot. Please come to an agreement and help save thousands of lives."
Monitoring group the Syrian Observatory for Human Rights said the evacuation from Foah and Kefraya, which are home to some 20,000 people, was expected to start on Saturday.
Syrian state TV, meanwhile, said starting the Idlib evacuations was the main condition for allowing the Aleppo exodus to continue.
A military news outlet run by the pro-government Lebanese Shia militia Hezbollah said buses had been taken to the two towns.
- BBC / Reuters