Aleppo, Syria - Deadly clashes erupted in Syria's Aleppo on Wednesday and a deal for the evacuation of rebel areas was on hold, leaving thousands of cold and hungry civilians uncertain of their future.
Entire families had gathered in the early hours, in the hope of leaving Aleppo after an agreement announced the night before for rebels to withdraw from the city.
But the first expected departures around 5:00 am (0300 GMT) were delayed and, a few hours later, fierce fighting again began to shake the city.
The landmark deal - which would mark the end of opposition resistance in Syria's second city after years of fighting - appeared increasingly precarious as the regime, the rebels, and their foreign allies traded accusations.
The last pocket of rebel-held territory in east Aleppo came under heavy tank fire, said an AFP correspondent in the area, who saw several wounded civilians.
The Syrian Observatory for Human Rights said air strikes had also hit rebel areas and that there were "very intense clashes on every front line".
State television said rebel rocket fire on government-controlled areas had also resumed, with at least seven people reported dead.
Rebels and a source close to the regime told AFP that the evacuation had been suspended after objections from Syria's government.
The source said Damascus had baulked when the rebels wanted to increase the number of those to be evacuated from 2,000 to 10,000.
But Yasser al-Youssef, a political official from the Nureddin al-Zinki rebel group, said the regime and its ally Iran were trying to add "new conditions" to the agreement.
"They want to link this deal to other issues, including the areas of Fuaa and Kafraya," he added, referring to two government-held Shiite-majority villages in northwestern Syria that are under rebel siege.
Moscow, a key Assad ally that launched an air war in support of his forces last year, said the Syrian army had resumed its operations in Aleppo after "an attack by the terrorists was warded off".
Ankara accused Assad's regime and its supporters of hampering the implementation the evacuation deal.
"The regime and some separate groups are trying to prevent this," Turkish Foreign Minister Mevlut Cavusoglu told reporters.
"There's Russia here, Iran, powers backed by Iran, and of course the regime. We expect nobody should blame each other on such a humanitarian issue," Cavusoglu said.
Before the fighting resumed, AFP's correspondent had seen crowds of civilians gathered in the streets of rebel areas from the early hours, some clutching bags of belongings, to await evacuation.
Some had slept in the open, despite the cold and a fierce storm that brought heavy rain and high winds, and most had gone without a regular meal in weeks.
The deal was announced a month into an army operation to recapture all of Aleppo that has seen the government take more than 90 per cent of the eastern districts rebels had held.
Brokered by Russia and Turkey, it was to see civilians and fighters leave Aleppo for opposition territory elsewhere in northern Syria.
Turkey said those leaving would be taken to Idlib province, which is controlled by a powerful rebel alliance that includes Al-Qaeda's former affiliate Fateh al-Sham Front.
The agreement came amid mounting international concern about the plight of civilians and as the UN said it had reports of atrocities being committed by advancing government forces.
The UN has reported allegations that men have gone missing after crossing to government areas, and on Tuesday said it had credible reports of summary executions by pro-regime fighters.
UN rights office spokesman Rupert Colville described reports of at least 82 civilians, including 11 women and 13 children, being executed in recent days.
He said pro-government fighters had reportedly entered homes and killed those inside, and "caught and killed on the spot" fleeing civilians.
Losing their onetime bastion will deal the opposition its worst blow since the conflict began in March 2011 and mark a major victory for Assad.
Aleppo, a cultural and economic hub second only to Damascus in importance, had been split between a rebel-controlled east and government-held west since 2012.
It was unclear how many civilians remained in rebel territory, after an estimated 130,000 fled to other parts of Aleppo during the government advance.
The assault has been accompanied by heavy air and artillery bombardment and more than 460 civilians have been killed in east Aleppo since it began in mid-November, according to the Observatory.
Another 130 have been killed by rebel rocket fire on western districts, it says.
More than 310,000 people have been killed since the Syrian conflict began, and over half the population has been displaced, with millions becoming refugees.