The sound of gunfire was reported on the streets of Cairo by residents, according to the al-Jazeera satellite network, dpa reported.
Protesters are continuing to defy curfew orders in Cairo, which have entered into effect and are set to last until dawn. Protesters are burning police stations and offices of the ruling party.
The residents quoted by the satellite network said the military had fired the shots after protesters tried to climb onto army vehicles, which were rolled out to enforce the curfew.
Earlier in the day, protesters successfully climbed on top of police vehicles and even overran police forces in some cities.
Egypt's powerful military had over the first four days of protests declined to get involved, allowing police and the Interior Ministry to attempt to manage the situation.