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:
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.