CAIRO - Egypt was on edge on Thursday after the Muslim Brotherhood warned of "confrontation" between the people and the ruling generals unless its candidate is named to succeed toppled president Hosni Mubarak.
A delay in announcing official results from the presidential election runoff, which had been due on Thursday, heightened the Brotherhood's fears of a "soft coup" by the military, which already disbanded the Islamist-led parliament and gave itself sweeping powers.
A senior Brotherhood official warned the ruling Supreme Council of the Armed Forces that it risked a "confrontation" with the people if Mubarak's last prime minister Ahmed Shafiq was declared the winner over the Islamists' Mohamed Morsi.
Returning officers had handed stamped results to representatives of the rival candidates after completing their tallies, which Morsi's campaign has made public. But only the electoral commission can declare the official result.
The commission said late on Wednesday that it would delay its announcement while it studied allegations of fraud from both candidates that might affect the final outcome of the June 16-17 runoff.
Shafiq's campaign team, which insists their candidate won the runoff despite the Brotherhood's claims of victory within hours of the close of polls, accuses Morsi's camp of printing almost one million false ballots, the state-owned Al-Ahram newspaper reported.
Morsi's campaign, which has published the results from counts 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 an open-ended 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.
They cite the military's assumption of legislative powers after a court ordered the Islamist-led parliament dissolved, and decrees giving the army powers of arrest and a broad say in government policy.
US Secretary of State Hillary Clinton said on Wednesday that it was "imperative" that the military follow through on its promise of a swift handover to civilian rule.
Some of the actions by the military leadership in recent days were "clearly troubling," said Clinton, whose government gives Egypt more than one billion dollars a year, mostly in military aid.
The generals say they have no intention of remaining in power after a civilian president takes office for the first time since the February 11, 2011 overthrow of Mubarak.
The ousted strongman is currently in a coma in a military hospital after suffering a stroke that prompted his transfer from a Cairo prison where he was serving a life sentence, military and medical sources said.
"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 assume 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 (the 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, as warning that there could be "a confrontation between the military and the people," should Shafiq be announced the winner of the presidential election.
"The insistence by Shafiq's campaign that he won indicates bad intentions from the military council and the electoral commission," he said.
Human Rights Watch said the decrees issued by the military over the past month cast doubt on the genuineness of its repeated pledges to hand over to a civilian president.
"These decrees are the latest indication yet that there won't be a meaningful handover to civilian rule on June 30," the New York-based watchdog's Middle East director Joe Stork said.