An Islamist backed by the Muslim Brotherhood declared victory as Egypt's first democratically elected president even as the country's military rulers issued a decree that virtually stripped the position of power.

The move by the Supreme Council of the Armed Forces - the military rulers in control since the ouster of Hosni Mubarak - came Sunday at the conclusion of a two-day presidential runoff, adding to the political turmoil that raised questions about the stability of the fragile democracy.

The military council will release details of an interim constitutional declaration on Monday morning, said Maj. Mohamed Askar, the council's spokesman.

Under the declaration, Askar told CNN, the military council retains the power to make laws and budget decisions for the country until a new constitution can be written and a new parliament elected.