Anti-Muslim Brotherhood protesters set a Freedom and Justice Party headquarters in Daqahliya's Aga on fire using petrol bombs, al-Jazeera Mubasher Misr reported on Friday.
The demonstrators tried to prevent fire engines from approaching the torched building, the Middle East News Agency reported.
Police interfered to allow the fire engines to pass through and put out the fire.
Torching the Brotherhood's headquarters coincided with an exchange of stones between protesters and the group's members who were inside the headquarters.
Thirty-two people were injured and transferred to hospitals.