The final vote on Egypt's new Islamist Constitution is this weekend.
The opposition, led by the National Salvation Front, says the new Constitution will suppress women, minorities, and lead to more violence.
Supporters of President Mohammed Morsi, a long-time member of the Muslim Brotherhood, and his opponents are clashing in the streets.
In the port city of Alexandria, police fired tear gas Thursday to separate Salafists and Muslim Brotherhood from Egyptians opposed to the Islamist takeover. Both sides pelted each other with rocks and stones.
Chanting "Allahu Akbar" (Allah is greater) and "with blood and soul we redeem Islam," Morsi's supporters called for a "million-man rally to defend clerics and mosques" on Friday," Fox News reported.
Christians in southern Egypt say they've been intimidated and blocked from voting by the Muslim Brotherhood. Residents in some villages say they were pelted with stones when they tried to vote last weekend.