Egypt's prosecutor ordered on Monday the arrest of five leading activists accused of inciting violence against the Muslim Brotherhood last week in Cairo, dpa reported.
Clashes erupted on Friday between Brotherhood opponents and supporters, who gathered to protect the group's headquarters in Cairo against protesters. More than 100 people were injured in the violence.
The five included leading blogger Alaa Abdel-Fattah, and activist Ahmed Douma, who both played a key role in mobilising mass protests that forced Hosny Mubarak out of power in 2011.
A statement said they were accused of inciting "violence, the destruction of property and disturbing peace in the events that erupted during the protest in front of the Muslim Brotherhood's headquarters."
The arrests come a day after President Mohammed Morsi, from Egypt's largest Islamist group, said he would take the necessary measures "to protect the nation" against anyone proved to be involved in violence.
The Brotherhood earlier Monday filed a legal complaint against 169 people, including politicians, accusing them of involvement in the violence.
Egypt's secular-led opposition accuses Morsi of tightening his Brotherhood's grip on power.