The planned evacuation of rebel districts of Aleppo stalled on Wednesday as air strikes and heavy shelling hit the city and Iran put new conditions on the deal.
Iran, a key backer of the Syrian regime, wants a simultaneous evacuation of wounded from the villages of Foua and Kefraya that are besieged by rebels, according to opposition and UN sources.
The Syria regime resumed shelling opposition-held parts of eastern Aleppo early on Wednesday, ending several hours of relative calm after a deal to evacuate civilians and rebels was announced.
"This morning regime forces fired at least 14 shells onto the area held by the rebels for the first time since Tuesday," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights.
Turkey accused the Assad regime and its allies of hampering the implementation of the deal.
"We now see that the (Syrian) regime and some separate groups are trying to prevent this (agreement)," Turkish Foreign Minister Mevlut Cavusoglu told reporters. "The evacuation could not take place in the full sense."
Turkey brokered the ceasefire deal with Russia late on Tuesday. The deal followed reports that regime forces and its militia allies had slaughtered 82 civilians, including women and children, in the days before Tuesday's pause of hostilities in eastern Aleppo.
TRT World's Shamim Chowdhury has this story about the plight of civilians still in Aleppo.