Thousands of activists occupy streets in Cairo close to an army base where many believe the disposed leader is being held.
Spokesman Gehad El Haddad called on all Egyptians to join them:
We are against violence.
The power of our cause is the power of democracy against a military coup.
But if our blood is the price we must pay to wake the conscience of the nation, and the conscience of the world, we would happily give it.
Inside the nearby Rabaa Adawiya Mosque, we found the senior Muslim Brotherhood leader, Mohammed Beltaji. The new authorities have issued a warrant for his arrest.
"We have our president in jail. Our leaders in jail. This is a struggle to return Egypt to legitimate government", he told us.
Many expect Friday prayers to act as a further flashpoint tomorrow.
Clashes over the past week have left more than a hundred dead, mostly supporters of the brotherhood.