Violence broke out on Friday between supporters and opponents of Islamist President Mohamed Morsi in Egypt's second city of Alexandria, leaving at least 10 people injured, a security official said.
The offices of the Freedom and Justice Party, the political arm of Morsi's Muslim Brotherhood, were also set on fire during the confrontations, the FJP said.
"The clashes erupted between the two sides and at least 10 people were injured because of rock throwing," the official told AFP.
Television footage showed protesters running in several directions in the Sidi Gaber area of Alexandria. Gunshots could be heard.
It also showed plumes of smoke rising from the FJP headquarters in the same neighbourhood.
Police reinforcements have been sent in to disperse the protesters, the official said.
The clashes come as pro- and anti-Morsi protests were staged around the country, two days ahead of planned mass rallies to call for Morsi to step down.