Egypt is braced for drama after Friday prayers as the vanquished Muslim Brotherhood called for a "day of rejection" following a widespread crackdown on its leadership by the country's new interim president, Adly Mansour.

Supporters of the ousted president, Mohamed Morsi, still reeling from the military coup that removed their leader from power, have begun to gather at rallies following a series of raids and arrests that decimated the Muslim Brotherhood's senior ranks and consolidated the military's hold on the country.

A Brotherhood statement read to supporters near the Rabia al-Adawiya mosque in eastern Cairo said: "We declare our complete rejection of the military coup staged against the elected president and the will of the nation. We refuse to participate in any activities with the usurping authorities."