Protesters flooded Cairo's Tahrir Square on Friday in the second giant rally this week, angrily vowing to bring down a draft constitution approved by allies of Egypt's President Mohammed Morsi, as Egypt appeared headed toward a volatile confrontation between the opposition and ruling Islamists.

The protests have highlighted an increasingly cohesive opposition leadership of prominent liberal and secular politicians trying to direct public anger against Morsi and the Islamists — a contrast to the leaderless youth uprising last year that toppled autocrat Hosni Mubarak.

The opposition announced plans for an intensified street campaign of protests and civil disobedience and even a possible march on Morsi's presidential palace to prevent him from calling a nationwide referendum on the draft, which it must pass to come into effect. Top judges announced Friday they may refuse to monitor any referendum, rendering it invalid.

Islamists are gearing up as well.

The Muslim Brotherhood, from which Morsi hails, drummed up supporters for its own mass rally Saturday. Islamists boasted their turnout would show the public supports Morsi.

The week-old crisis has already seen clashes between the two camps that have left two dead and hundreds injured. On Friday, Morsi opponents and supporters rained stones and firebombs on each other in the Mediterranean city of Alexandria and the southern city of Luxor.

Rushed vote on constitution draft

The Islamist-led assembly that worked on the draft for months passed it in a rushed, 16-hour session that lasted until sunrise Friday.

The vote was abruptly moved up to pass the draft before Egypt's constitutional court rules on Sunday whether to dissolve the assembly. Liberal, secular and Christian members had already quit the council to protest what they call Islamists' hijacking of the process.

The draft is to be sent to Morsi on Saturday to decide on a date for a referendum, possibly in mid-December.

The draft has a distinctive Islamic bent — enough to worry many that civil liberties could be restricted, though its provisions for enforcing Shariah, or Islamic law, are not as firm as ultraconservatives wished.

Protests began last week when Morsi issued decrees granting himself sweeping powers that neutralized the judiciary. Morsi said the move was needed to stop the courts — where anti-Islamist or Mubarak-era judges hold many powerful posts — from dissolving the assembly and further delaying Egypt's transition.

However, opponents accused Morsi of grabbing near-dictatorial powers by sidelining the one branch of government he doesn't control.

Opposition leadership emerges

Friday's crowd in Tahrir appeared comparable in size to the more than 200,000 anti-Morsi protesters who thronged the central plaza three days earlier. Tens of thousands more marched Friday in Alexandria and other cities.

Figures from a new leadership coalition took the stage to address the crowds. The coalition, known as the National Salvation Front, includes prominent democracy advocate Nobel Peace laureate Mohamed ElBaradei, leftist Hamdeen Sabbahi and former Arab League chief Amr Moussa.

The coalition is aiming to rally together the disparate opposition factions, hoping to focus a movement that critics say failed to capitalize on its gains after Mubarak's fall. That they appear to have won a degree of acceptance among protesters is a significant shift, since mainstream liberal politicians were dismissed by many activists as out of touch, disorganized and out for their own interests.

ElBaradei's strong move to the fore is particularly notable. He was an inspiration for some of the youth in the 2011 anti-Mubarak uprising, but long appeared reluctant to play a leadership role and was criticized as remote and elitist.

The politicians still lack grassroots, warned Manal Tibe, a rights activist who was the first member of the constitutional assembly to withdraw in protest against the Islamists. Some protesters worry they won't push strong enough demands, she said.

If the charter does go to a referendum, the politicians do not have the public reach or enough time to galvanize a "no" vote, said protester Mohammed Taher, 45.

Opposition can boycott, rally 'no' vote for referendum

Members of the constitutional assembly in Cairo vote on a final draft of a new Egyptian constitution. (Mohammed Abu Zaid/Associated Press)

The opposition also is counting on a revolt by the judiciary. Many judges have gone on strike, raising the possibility they would not serve as election monitors as required. Two top judicial bodies, the High Administrative Court and the State Council, said they would confer with the main judges' association on whether to monitor.

But if a referendum is held, the opposition faces the tough choice of whether to boycott — and risk sidelining itself — or trying to rally a "no" vote — and risk losing in the face of Islamists' powerful grassroots electoral machine.

The Brotherhood and harder-line Islamists won nearly 75 per cent of the seats in last winter's parliament election. However, Morsi, who is backed by the Brotherhood, won only about 25 per cent in a first-round presidential vote and just over 50 per cent in the runoff.

Safwat Hegazy, a hardline cleric allied to the Brotherhood, challenged the opposition in a Tweet to "go to the people in the referendum … If the people are by your side and say no, we'll know who you are and who we are."