Egypt was on edge Thursday after the Muslim Brotherhood declared an open-ended protest and warned of "confrontation" unless their candidate is named new president to succeed toppled dictator Hosni Mubarak.
The delay in announcing the results, due Thursday, of the June 16-17 presidential vote heightened the Brotherhood's fears of a "soft coup" by the military, which disbanded the Islamist-led parliament and gave itself sweeping powers.
A senior member of the Islamist movement, which says its candidate Mohamed Morsi won last weekend's vote, warned the ruling generals of a "confrontation" with the people if rival candidate Ahmed Shafiq was announced the winner.
The electoral commission late on Wednesday said it would delay announcing the result, which had been scheduled for Thursday, as it studied allegations of fraud from both candidates that might affect the final result.
Shafiq's campaign, which insists their candidate, Hosni Mubarak's last prime minister, won the run-off election, accuses Morsi's camp of printing almost one million false ballots, the official Ahram newspaper reported.
Morsi's campaign, which has published the results from counting stations across the country, denies the allegation and accuses Shafiq's team of bribing voters.
The newspaper of the Brotherhood's political arm, the Freedom and Justice Party (FJP), ran a large red banner on its Thursday edition saying, "Sit-in" above an announcement of a protest until Morsi is sworn in.
The military has pledged to hand power to the winner by the end of the month, but Brotherhood members who set up tents in Cairo's Tahrir Square, the hub of protests that overthrew Mubarak last year, say they are not convinced.
The generals say they have no intention to remain in power after the new president takes office for the first time since the February 11 2011 overthrow of Mubarak, who is reported to be in a coma in a military hospital.
A court sentenced the former leader to life in prison earlier this month but he was transferred to hospital on Tuesday after suffering a stroke.
"This is a constitutional coup," said Brotherhood member Abdel Rahman al-Saoudi, one of the protesters camped out in Tahrir on Thursday morning, adding he would not leave the square until Morsi's inauguration.
The protesters also demand the military repeal an updated interim constitution that allows it to take over parliament's powers and gives it a say in drafting the country's next constitution.
The sit-in comes after the Brotherhood held a large rally in Tahrir Square on Tuesday.
"We insist on remaining in the square until we achieve the goals of the revolution and the demands of (Tuesday's rally): confronting the military coup against legitimacy," the FJP's website quoted senior leader Essam al-Erian as saying.
The website also quoted Mahmud Ghozlan, a member of the Brotherhood's politburo, warning there could be "a confrontation between the military and the people" should Shafiq be announced the winner of the presidential elections.
"The insistence by Shafiq's campaign that he won indicates bad intentions from the military council and the election commission," he said.