"An ammunition dump exploded in a barracks at 4:30am (01:30 GMT). There are deaths and casualties among soldiers," the official said.
One witness, who declined to be named, said: "The blast was huge. One hospital I went to was filled with injured personnel."
Most of the injured were treated on the spot from "minor wounds" caused by shattered glass.
An official at Aleppo University Hospital said the bodies of five dead soldiers and 10 wounded were brought to the facility.