The Syrian government while accusing the rebels of breaking the terms of deal suspended the evacuation of civilians and fighters from eastern Aleppo.
There are unconfirmed reports that blasts were heard in the area where evacuees were boarding buses.
More than 3,000 were taken out of eastern Aleppo through buses on Thursday, but the UN says at least 50,000 are still trapped.
Syria’s army, backed by Russia, has taken nearly all rebel-held districts.
