Hundreds of supporters of Islamist President Mohamed Morsi protested Sunday outside a top Egyptian court, forcing judges to delay a hearing on a constitutional panel at the heart of a deepening crisis.

The Supreme Constitutional Court could not even begin sitting when it called an "administrative delay" to the session that would have also looked into the status of the Islamist-dominated senate, a judicial official said.

Any rulings would have escalated a crisis with Morsi, who in a decree expanding his powers barred the court from examining the case, before the panel adopted the constitution on Friday.

Both the judicial official and state television did not say when the court would hold any new session.

The Islamists, many wrapped in blankets and carrying posters of Morsi, had spent the night outside the courthouse in a bid to prevent its judges from entering.

The disputed draft constitution -- which declares "the principles of Islamic sharia" as the main source of legislation -- is to be put to a referendum on December 15.

It has fuelled the country's worst political crisis since Morsi's election in June, squaring Islamist forces against secular-leaning opponents.

Mass rival rallies preceded Morsi's referendum announcement on Saturday, a day after crowds thronged to Tahrir Square to denounce his "dictatorial" decree.

"One nation, two peoples," read the front page of Al-Shuruq newspaper, while Al-Masri al-Youm ran with "Egypt at the mouth of a volcano".

Sunday's session on the legality of the constituent assembly, which drafted the new charter amid a boycott by secularists, liberals and Christians, would have defied a presidential decree barring any judicial body from dissolving the panel.

The protesters surrounded entrances to the courthouse and blocked off a main road that runs along the Nile leading up to it, trying to prevent the judges from entering, a correspondent said.

"The will of the people is stronger than the will of a few judges," said demonstrator Ismail Ahmed, 39, referring to the judiciary that contains many judges left over from former strongman Hosni Mubarak, who was ousted by a popular uprising last year.

Hundreds of thousands of Islamist protesters gathered on Saturday in support of Morsi, his sweeping powers and the disputed constitution.

Morsi's November 22 decree sparked the crisis, with the constitution, which had been due for more deliberation, being rushed through days later amid popular unrest.

The Muslim Brotherhood and their supporters have branded the anti-Islamist opposition enemies of the 2011 revolution.

Sunday's protesters also chanted against secular and liberal opposition leaders.

The National Rescue Front -- a coalition of opponents led by Mohamed ElBaradei, the former UN nuclear watchdog chief; ex-Arab League chief Amr Mussa; and former presidential candidate Hamdeen Sabbahi -- has called on opponents of the decree to maintain the pressure.

Islamist protests have rivalled those by Morsi opponents, who massed in Tahrir Square on Friday to demonstrate against the constitution.

Human rights activists have slammed the draft charter.

Joe Stork of Human Rights Watch said: "Rushing through a draft while serious concerns about key rights protections remain unaddressed will create huge problems."

Amnesty International said the draft "raises concerns about Egypt's commitment to human rights treaties," specifically ignoring "the rights of women (and) restricting freedom of expression in the name of religion".

On Thursday, Morsi stressed his new powers would expire once the constitution was ratified, a point Islamists have repeatedly made in his favour.

In 2011, the Brotherhood and the secular-leaning opposition stood side by side in Tahrir Square as they fought to bring down Mubarak and his regime.

But since Mubarak's downfall in February 2011, the Islamist movement has been accused of monopolising power.