EGYPT'S military has brought in reinforcements of troops and armour to bases near Egyptian cities ahead of Sunday's protests.
The mass rallies have been planned by the opposition to try to force the Islamist president out.
Clashes between supporters and opponents of President Mohammed Morsi erupted yesterday, killing at least two people.
Some Islamists accuse activists of paving the way for a coup, a charge that the opposition vehemently denies.
With Egypt gripped by fears of a showdown between Islamists and their opponents, security sources said 90 people were wounded in the city of Mansoura after hundreds of men were involved in rock-throwing street skirmishes.
Witnesses heard gunfire and state television showed a man in hospital with birdshot wounds.
Similar outbursts of violence, often prompted by one side or the other staging rallies, have hit towns across the country in recent days.
At least two men died last weekend. The opposition plans mass protests this weekend, calling for Mr Morsi to resign.
He shows no sign of doing that and is expected to blame the deadlock that has aggravated an economic crisis on resistance from those loyal to his ousted predecessor Hosni Mubarak.