“The army has no role in ruling people. Its only job is to protect the country. We want civilian rule chosen through democracy,” said Hani Hegazi, a 28-year old Brotherhood member who traveled by bus to Tahrir from the Delta province of el-Beheira, according to The Associated Press.

Banners read: “Down with military rule. Egypt our country is not a military camp.” Some demonstrators flew the Egyptian flag, while others including ultraconservative Salafis waved a banner declaring Islam's holy book, the Quran, to be “our constitution.”

The rally was called to protest a document floated by the government which declares the military the guardian of “constitutional legitimacy,” suggesting the armed forces could have the final word on major policies even after a new president is elected. The document, which includes guiding principles for Egypt's new constitution, also introduces clauses that would shield it from civilian oversight.

Most of Egypt’s pro-democracy groups object to the document, calling it an attempt to perpetuate military rule past the post-Mubarak transitional period which is supposed to end with the election of a new parliament and a new president.

Delivering the Muslim prayer sermon, imam Mazhar Shahin urged protesters to keep defending the goals of the revolution.

“Perhaps those who rule us think we will forget our cause with the passage of time. They are deluded and mistaken,” he warned the ruling Supreme Council of the Armed Forces (SCAF), which took power when Mubarak was ousted.

“We reject the imposition of dictates on the people, we reject Silmi’s document. No voice can drown out the voice of the people,” Shahin told the crowd.

“Those who fear Islamist movements in Egypt, I tell them don’t be scared of Islam in Egypt,” Shahin said, AFP reported.

“Egypt is Islamic, like it or not... We want a civic democratic state with an Islamic vision that allows people to practice their rights and democracy,” he said.

In addition to the Brotherhood, Salafis, left- and liberal-leaning groups such as the April 6 movement and other youth revolutionary alliances have joined the rally, demanding a timetable for the end of military rule which began in February.

They have called for marches from mosques around Egypt to major squares, dubbing it the “Friday of the Single Demand” - that demand being a clear date for the transfer of power to civilian rule. Many groups have planned to hold an open ended sit-in until a date has been set.

The Brotherhood says the document reinforces “dictatorship.”

“It contains articles that rob the people of their sovereignty and reinforces dictatorship. It constitutes a coup against the principles and goals of the January 25 revolution,” the group said in a statement issued Wednesday. Last minute negotiations between the government and the Brotherhood failed to stave off their participation in the rally, or scrap the document.

Close by, the head of the fundamentalist Gamaa Islamiya, Tarek al-Zomor, told AFP that the constitutional principles were a "circumvention of the people’s will.”

“We are here to stress the necessity of a timetable to civilian rule. If that doesn’t happen, then it confirms the conspiracy to rob the revolution,” Zomor added.

The show of force comes 10 days before the country’s first parliamentary elections since Mubarak stepped down, when a Brotherhood-affiliated political party is expected to fare well.

Anger against the Supreme Council has been building up over their management of the transition period. Many complain that the generals are recreating the Mubarak regime by cracking down on opponents, by refusing to order a thorough reform of the security services, and by monopolizing decision making. Islamists and liberals alike now express fear that the military council wants to hold on to power, a claim denied by the generals.

The military council had promised to transfer power to an elected civilian government within six months of Mubarak's ouster. But according to a vague timetable in place, it may not be until early 2013 that a president is elected. Only the dates for the parliamentary elections, which are due to begin in ten days and which will drag into March, are yet known.

Walid Farouk, 32, who wore the heavy beard and traditional robe of the ultraconservative Salafi trend, said that Egypt had seen nothing good from military rule since the army took power in 1952.

“All of us are scared that the army could try to hold on to power,” he told AP. “It is time for a civilian government.”

The writing of Egypt’s constitution has been a divisive issue, and details of who will write it and what it contains are at the heart of the recent rally.

Some liberals have supported the idea of writing guiding principles for the constitution, fearing that a parliament controlled by Islamists would insert religious principles into the document.

Even now, some liberals remain opposed to the Friday rally, saying a document is necessary to detail how members of the assembly are to be chosen, and controversial clauses can be negotiated.

But many others have come to distrust the military’s Supreme Council at least as much they distrust the Islamists.

At the rally, protesters are expected to celebrate the birthday of one of the most prominent revolutionary to be jailed by the military prosecutor. Alaa Abdel Fattah, a famous blogger and activist, was detained late last months for refusing to answer to the military prosecution on his alleged role in sectarian violence that left 27, mostly Christians, dead. He turns 30 Friday.

Many hold the military responsible for the violence, and see Abdel-Fattah's detention as an attempt to find a scapegoat and discredit activists.