Cairo (CNN) -- 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 stripped the position of much of its power.

The move by the Supreme Council of the Armed Forces -- who have run Egypt since the ouster in February 2011 of Hosni Mubarak -- came Sunday at the conclusion of a two-day presidential runoff.

Even with no constitution, no parliament and, possibly, little power, the Muslim Brotherhood's Mohamed Morsi declared victory late Sunday over Ahmed Shafik, who was Egypt's prime minister in the final days of the regime of Mubarak.

Unofficial results released Monday by the state-run Al-Ahram news website showed Morsi with 11.2 million votes, or 52.3%, compared with 10.3 million for Shafik.

Shafik did not concede, saying votes had not yet been tallied in his stronghold districts, including portions of Cairo.

Whoever emerges as the winner, his power will be limited.