Tens of thousands of people have gathered in Cairo's Tahrir Square to protest against Egyptian president Mohamed Morsi, in one of the biggest gatherings since the dictator Hosni Mubarak was forced from office.

Protesters are angry Mr Morsi has issued a decree barring any sort of court review of his decisions.

The decree put him on a collision course with the judiciary, and consolidated the long-divided opposition that accuses him of taking on dictatorial powers, and raises concerns that the Islamists will be further ensconced in power.

"I'm here to protest Morsi's autocratic decisions," said Mohammed Rashwan, an engineering graduate who voted for Mr Morsi in the country's first presidential election since a popular uprising toppled Hosni Mubarak last year.

"I have discovered that he is pro-Muslim Brotherhood and not the revolution."

Throughout the afternoon and into the evening, marchers poured into Tahrir Square, swelling the numbers, amid an electrifying atmosphere many said reminded them of the 2011 uprising.

While Mr Morsi has agreed with the nation's top judges to limit the use of his new powers he has refused to rescind his decree.

That has sparked a rare common sense of purpose amongst his opponents and the centre of Cairo is now echoing with calls for his downfall.

The huge turnout in the iconic square in the heart of Cairo, as well as in the Mediterranean city of Alexandria and most of Egypt's 27 provinces, marked the largest mobilisation yet against the president.

'Cancel the constitutional declaration'

A protester throws a tear gas canister during clashes with riot police in Tahrir Square.. ( Reuters: Mohamed Abd El Ghany )

The demonstrations come a day after the president stuck by his decree after a meeting with the country's top judges aimed at defusing the crisis that has sparked deadly clashes and prompted judges and journalists to call for a strike.

"The solution is to cancel the constitutional declaration ... We won't replace a dictator with another," said Asser Ayub, 23, waving an Egyptian flag.

In the Mediterranean city of Alexandria, thousands gathered in Qait Ibrahim square.

Members of the Muslim Brotherhood, on whose ticket Mr Morsi ran for office, staged their own rival rally, but marched away after a few hours without any confrontations.

"Down with the rule of the Supreme Guide," the protesters chanted, in reference to the head of the powerful Islamist group, a chant echoed in the Red Sea resort of Sharm el-Sheikh, where hundreds took to the streets.

Demonstrations were also staged in the Nile Delta cities of Mansura, Tanta and Mahalla and in the central provinces of Assiut, Sohag and Minya

A rival rally in Cairo by the Muslim Brotherhood in support of the president was called off to "avoid potential unrest" but that has done little to abate the division among supporters and foes of Mr Morsi.

"The Muslim Brotherhood stole the revolution" read one banner in Tahrir.

Three people have died in clashes since Mr Morsi decreed his new powers on Thursday.

Morsi stands firm

Protesters chant anti-government slogans in Tahrir Square ( Reuters: Mohamed Abd El Ghany )

After the meeting on Monday with top judges, Mr Morsi stuck by his controversial decree.

There was "no change to the constitutional declaration," presidential spokesman Yasser Ali told reporters at the end of the meeting.

But he added Mr Morsi sought to clarify that any irrevocable decisions apply only to issues related "to his sovereign powers" and stressed the temporary nature of the decree.

In a statement, the head of the Freedom and Justice Party (FJP) - the political arm of the Muslim Brotherhood - said the meeting between Mr Morsi and the judges had been "fruitful".

But judges at the meeting said the crisis was not over.

"The meeting failed," Judge Abdel Rahman Bahlul, who attended the talks, told the independent daily Al-Masry Al-Youm.

"We cannot say this is the end of the crisis between the judiciary and the presidency," another judge who attended the talks, Judge Ahmed Abdel Rahman, told the paper.

Mr Morsi's decree has led to charges that he is taking on dictatorial powers.

The decree also bans any judicial body from dissolving a controversial panel that is drafting the country's new constitution.

Liberals, leftists and the country's three churches have already walked out of the Islamist-dominated panel because they say it fails to represent all Egyptians.

ABC/AFP