Egyptian protesters have occupied Cairo's Tahrir Square for the first time in months as they press for the release of the country's presidential election results.

People filled the square, at the heart of the uprising that led to the toppling of former president Hosni Mubarak, after the country's military rulers said the release of the weekend's balloting, which had originally been set for Thursday, was  postponed.

Both candidates — Mubarak's last prime minister, Ahmed Shafiq, and Mohammed Morsi of the Muslim Brotherhood — have claimed victory.

In downtown Cairo, the newspaper headlines told the story of a country wound up tight, CBC's Derek Stoffel reported.

"Egyptians are about to explode," declared one of the papers.

All night long, demonstrators chanted in Tahrir Square, railing that the ruling military council has brought back martial law and that the generals have given themselves sweeping new powers.

The delay in the presidential voting results added to the protesters' concerns.

"This means there is an intention to rig the election," said demonstrator Sherif Mohamed. "There is an intention to betray the elected president."

Delay raises question marks

The elections commission says it needs a few more days to investigate several hundred claims of voting irregularities raised by the two candidates in the race.

"I have faith in the judges of Egypt, but too much delay will raise question marks," Saad el-Katatni, a senior Brotherhood leader and speaker of the dissolved legislature, told Al-Jazeera in an interview. "The result is already known and it is Mohammed Morsi."

Late Thursday, Shafiq repeated his claim of victory and charged that the Brotherhood was "playing games" and striking "backdoor deals" with outside powers to influence the results.

Shafiq denounced the Brotherhood's public appeals. "These protests in the squares and fear-mongering campaigns in the media are all aimed at putting pressure on the election commission," he said.

Egypt's media are demonizing 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 Brotherhood escalated its fight with the military, calling for a mass protest Friday to denounce what it called a power grab by the generals. Three major Islamist groups said Thursday they would join the protest in Tahrir Square, birthplace of the uprising that forced Hosni Mubarak out of office last year.

International condemnation of the generals who took over from Mubarak also intensified. Human Rights Watch complained that recent moves by the military suggested that there would not be a "meaningful" handover of power to civilian rule by July 1 as promised and created conditions "ripe" for more human rights abuses.

The military has over the past week given itself the role of legislator, the right to arrest civilians and control over drafting a new constitution. It has also taken several steps to shield the military from civilian oversight.

"The generals' relentless expansion of their authority to detain and try civilians now goes far beyond their powers under Hosni Mubarak," said Joe Stork, the Middle East director of Human Rights Watch, said in a written statement.

His words echoed criticism by former U.S. president Jimmy Carter, a frequent visitor to Egypt who repeatedly met with its ruling generals, and Amnesty International.

The Brotherhood has said repeatedly it will not resort to violence if Shafiq wins, but it maintains that Mubarak's longtime friend and admirer could win only through fraud.

With files from The Associated Press