The head of Egypt's election commission says official results from the disputed presidential runoff vote will be released Sunday.

Farouk Sultan, the head of the Supreme Presidential Election Commission, confirmed the timing on Saturday.

Results of runoff vote between the Muslim Brotherhood's candidate Mohammed Morsi and a Mubarak-era politician Ahmed Shafiq were postponed last week as both campaigns claimed victory.

Demonstrators continued their sit-in into the fifth successive day on Saturday in protest against the disbanding of the Islamist-dominated parliament last week and calling for military leaders to rescind a constitutional declaration granting the generals sweeping powers and stripping the next president of much of his authority.

At stake is whether or not Egypt will emerge from the instability of the 16-month transition that followed Hosni Mubarak's 2011 overthrow, or whether the power struggles will continue or even escalate to a more dangerous level.

Tensions soared Wednesday 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 Shafiq, an ex-air force commander who many view as the military's preferred candidate, by 52 per cent to 48 per cent.

Shafiq has also claimed victory by a narrow margin.

The postponement of an official announcement set off a wave of charges of manipulation aimed at all sides, including the ruling military.

Generals accused of withholding results

The military had pledged to hand over power to civilian rule by July 1. But on June 15, the country's highest court dissolved the country's Islamist-led parliament, calling the law under which it had been elected unconstitutional. Two days later the generals issued a declaration in which they gave themselves legislative powers, including the right to draft a constitution.

Brotherhood leaders say the military is holding the election results hostage to get the movement to accept the power grab.

The Muslim Brotherhood escalated its fight with the military, calling for a mass protest on Friday to denounce what it called a power grab by the generals.

Egyptian supporters of the Muslim Brotherhood's candidate for president, Mohammed Morsi, attend Friday prayers in Tahrir Square. (Bernat Armangue/Associated Press)

Three major Islamist groups said they would join the protest in Tahrir Square, birthplace of the uprising that forced Hosni Mubarak out of office last year.

On Saturday, Maj. General Mahmdouh Shaheen, a member of the ruling council and its legal adviser, said there are no plans to amend the constitutional declaration entrenching the executive and legislative powers of the generals.

"There is no amending of the constitutional declaration. It is just like the constitution," he told The Associated Press.

Protesters were still in the square on Saturday morning, determined to see their demands met.

"The sit-in is open ended until the reversing of the supplement constitutional declaration, until the cancelling of the latest ministerial decision that gives wide powers to military officers to arrest civilians and the cancelling the disbanding the parliament," said Saied Zaki a supporter of the Muslim Brotherhood.

In not announcing the results when scheduled, the military declared it was acting for "higher national interests" and vowed to crack down on any violence by any group unhappy with the eventual electoral outcome.

Egypt's media are demonising the Muslim Brotherhood as the state's worst enemy, claiming the fundamentalist group plans to plunge the country into chaos if its candidate does not emerge as the winner from the presidential runoff.

The Muslim Brotherhood has said repeatedly that it would not resort to violence.

Brotherhood leaders said the ruling military council is holding the election results hostage as it bargains to maintain its lock on power.

Protester Walid Ahmed said the military council has too much to lose if it relinquishes its grip on power.

"The military is afraid to leave power because there are a lot of hidden mistakes they will be held accountable for," he said.

He added that protesters were concerned that if Shafiq won, the country would go back to where it was when the uprising began.

The military has blamed the Brotherhood indirectly for stirring tensions.

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."

The military's move has nonetheless brought many Egyptian critics of the Brotherhood to the side of the Islamist movement against what they now see as a larger threat: the entrenchment of military power.