Militia allied to the Syrian regime opened fire on a convoy as it prepared to leave rebel-held eastern Aleppo on Thursday.
Civil defence rescue officials said at least one person was killed. A reporter at the scene of the attack said four people were killed and several injured when Iranian-backed militia opened fire on the convoy.
The convoy was the first to leave the city after a new deal was struck overnight to evacuate injured civilians from eastern Aleppo. After the attack it returned to the Syrian city.
A separate evacuation of opposition fighters from Aleppo was also planned for Thursday. Russian soldiers were preparing to lead rebels out of Aleppo, the defence ministry in Moscow said. It said the Syrian regime had guaranteed the safety of the rebels and their families, who would be taken towards Idlib, a city in northwestern Syria.