Angry crowds broke into the Freedom and Justice Party (FJP) headquarters in Assiut and set the building ablaze Monday night after three protesters were killed in Sunday clashes with supporters of President Mohamed Morsi.
Al-Dostour Party in Assiut reported that crowds celebrated torching the building with fireworks and chants.
Protesters had gathered earlier in front of the governorate building where they had planned to stage a sit-in demanding the removal of Governor Yehia Keshk.
They barricaded the building, barring entrance to employees, and demanded that a member of the Armed Forces assume control of the governorate. Protesters set up a stage from which they issued statements and played patriotic songs.
Three protesters, Mohamed Nassef Shaker, Abanob Adel and Mohamed Abdel Hamid died during clashes on Sunday night.
According to Al-Dostour Party in Assiut, protesters near the governorate building were attacked by supporters of the FJP who were securing their party headquarters, one kilometre from the governorate building.
Funerals were held on Monday amid chants against the president, the Muslim Brotherhood and its supreme guide, Mohamed Badie.
Assiut prosecution ordered an investigation into the clashes, and local police arrested two on Monday near the FJP headquarters, including Islamist Osama Al-Nawasany, reported state-owned Al-Ahram.