CAIRO — Egypt’s military and the Muslim Brotherhood traded blame for rising tensions Friday as the country awaited the outcome of a presidential runoff vote that pits an Islamist against ousted leader Hosni Mubarak’s former prime minister.
Brotherhood leaders said the ruling military council is holding the election results hostage as it bargains to maintain its lock on power. Tens of thousands of Brotherhood supporters have rallied in the capital’s Tahrir Square in a show of force backing candidate Mohammed Morsi, who has warned against manipulating results in a vote that he said he has won.
The military declared it was acting for ‘‘higher national interests’’ and vowed to crack down on any violence by any group unhappy with the electoral outcome.
At stake is whether Egypt will emerge from the instability of the 16-month transition that followed Mubarak’s 2011 overthrow, or whether the power struggles will continue or escalate. The Brotherhood has said repeatedly that it will not resort to violence, but several media outlets have launched a vigorous campaign against the movement, saying it will plunge the country into chaos if Morsi does not win.
Tensions soared Thursday when the country’s military-appointed Election Commission indefinitely delayed announcing the results of the weekend elections. The Brotherhood announced soon after polls closed Sunday that it had beaten rival candidate Ahmed Shafiq, a former force commander whom many view as the military’s preferred candidate, by 52 percent to 48 percent. Shafiq has also claimed victory by a narrow margin.
Many accuse the military of planning to direct the election commission to announce a Shafiq win. Others say the commission has determined there was a genuine Shafiq victory but fears that no one will believe them. The commission says it is sorting out the accusations of election violations filed by both candidates.
The Brotherhood has raised another possibility: Just before the vote, the nation’s highest court dissolved the Brotherhood-led Parliament and the military granted itself new exceptional powers, leaving the next president with limited authority. The generals won’t let the commission announce Morsi’s victory until they accept those decisions, some movement figures say.
‘‘The military council is waging a psychological war and the delay in announcing the results is just part of it,’’ said Saad Emara, a Brotherhood member of the disbanded parliament.
The Brotherhood sent its supporters to the streets for the fourth consecutive day to protest the military’s power grab. On Friday, it was the biggest such rally, and protesters called on Morsi to be sworn in as president in Tahrir Square.
‘‘We are in the middle of a struggle of wills between the military and the Brotherhood [together] with the forces in the square. Each party is trying to use all their cards to put pressure on the other party, pushing to the brink, ‘‘said Mohammed Habib, former deputy leader of the Muslim Brotherhood, who resigned from the group a year ago.
The military has blamed the Brotherhood indirectly for stirring tensions. ‘‘Announcing the results of the presidential election early, before the official statement, is unjustified and is one of the main reasons behind the division and confusion prevailing on the political scene,’’ said a statement from the council read on state television. It did not mention the Brotherhood by name.
The military also defended its newly issued ‘‘supplementary constitutional declaration’’ that granted the generals sweeping powers, including legislative authority and approval of the budget. The declaration was met by condemnation both by Egyptian and by international groups, saying it raised doubts about the military’s commitment to transfer powers to an elected civilian authority by July 1.
The constitutional declaration was ‘‘a necessity’’ during this ‘‘critical period,’’ the military statement said. ‘‘Whatever decisions issued by the [military council] are guided only by higher national interests and not any other.’’
Leftists and secularists stood beside Morsi at a Friday news conference in which the Brotherhood leader said the military had ‘‘erred’’ in its recent decisions.
Wael Ghonim, a former Google executive and one of the leading figures behind the protests against Mubarak last year, was among those rallying behind Morsi. He said it was time to put political differences aside.
‘‘Our support is not to the Brotherhood, but to legitimacy and democracy against any attempts by anyone — either those with guns or those waging misleading media campaigns,’’ Ghonim said.
Out in the square, protester el-Sayyed Abdel-Razek said the military underestimates what will happen if it does not step aside in favor of a civilian government.
‘‘I want to tell [the head of the military council Field Marshal Hussein] Tantawi, you have no idea what will happen, if you don’t hand over power,’’ he said, speaking of a new mass uprising similar to the one that overthrew Mubarak. ‘‘These people in the square are all ready to die.’’