Tens of thousands of Egyptians gathered in Cairo’s Tahrir Square on Tuesday evening to accuse the ruling military council of mounting a “constitutional coup”.
Activists said the military had extended its own powers in an attempt to remain in charge following the presidential election.
Smaller groups of pro-democracy supporters rallied outside the Egyptian parliament, which was dissolved while the weekend runoff vote was underway.
Although official results are not expected until Thursday, both the Muslim Brotherhood’s candidate Mohamed Morsey and former Mubarak ally Ahmed Shafiq claim they have won.
Shafiq’s campaign spokesman told the media: “We have the correct figures; we are sure the next president of Egypt is General Ahmed Shafiq.
The military council, which took office following last year’s overthrow of Hosni Mubarak, said it will hand back powers to parliament and claims the president’s role has not been reduced to that of a mere figurehead.