Tear gas canisters rained down on a pro-Morsi march in the Sharq neighborhood in Alexandria, amid repeated bursts of automatic gunfire, an AFP correspondent said.
Hundreds of Morsi loyalists had marched through the city when police fired tear gas to disperse them.
Residents, armed with clubs, came out of their homes and shops to help the police, detaining Morsi supporters and handing them over to officers at the Sharq police station.
Morsi supporters, carrying Egyptian flags and pictures of the deposed leader, then clashed with his opponents on a road carpeted with rocks.
The violence in Alexandria comes hours after security forces stormed two pro-Morsi protest camps in Cairo, leaving scores dead.
Morsi, Egypt's first freely elected president, was ousted by the military on July 3 with popular backing.
Deep political divisions in the country intensified following his removal.
Supporters of the Islamist leaders have vowed to keep fighting for his reinstatement at any cost.
HH/HH