A number of Islamist groups are calling for a rally "to defend scholars and mosques" in front of the Qaed Ibrahim mosque in Alexandria on Friday.
The protest comes after Sheikh Ahmed El-Mahalawy was trapped inside the mosque for 14 hours on Friday by protesters angry at his sermon calling for a 'Yes' vote in the constitutional referendum.
Among the groups calling for the protest are the Muslim Brotherhood and its political arm the Freedom and Justice Party, the Salafist Calling, the Salafist Nour Party, the Asala Party, Al-Gamaa Al-Islamiya, and the Building and Development Party.
On Friday, clashes erupted in front of the Qaed Ibrahim mosque and along the nearby corniche between several thousand opponents and supporters of the draft constitution.
On Saturday, half the country voted on the constitution, while the second half will vote on 22 December.