Dozens set fire to the Muslim Brotherhood's Freedom and Justice Party's office in Gedeila, Mansoura on Friday.
Attackers emptied the office of contents before setting them, too, on fire.
Central Security Forces meanwhile dispersed four marches by the National Alliance in Support of Legitimacy, a group supporting the reinstatement of deposed President Mohamed Morsy
Forces fired tear gas on the marches.
The fourth march on Suez Canal street was attacked by assailants carrying bladed weapons and BB guns, which led to several injuries among the protesters. Security forces chased a number of protesters down nearby streets.
Morsy's Islamist backers had called for fresh protests on Friday to condemn his removal by the army in early July and the recent army crackdown on pro-Mory sit-ins which left hundreds dead.
Edited translation from Al-Masry Al-Youm
