An Egyptian activist who slipped into a coma following days in police custody died on Monday, the health ministry and his party said, setting off a storm over police brutality in the new Egypt.

Mohammed al-Guindi, 28, went missing last month after joining protests demanding change on the second anniversary of Egypt's uprising against former president Hosni Mubarak.

Egypt's top court on Sunday postponed a ruling on the legality of the Islamist-dominated commission that drafted a contested new constitution, state media reported.

A verdict on the constitution, adopted by referendum in December, had been due on Sunday but the Supreme Constitutional Court adjourned its decision until March 3, the reports said.

Sporadic clashes broke out overnight between protesters demanding the ouster of Egypt's Islamist President Mohammed Morsi and security forces outside the presidential palace, witnesses said on Sunday.

There were no immediate reports of casualties from the confrontations which follow violent clashes on Friday outside the presidential palace that left one person dead.

Egypt's main opposition group on Saturday backed calls to oust President Mohamed Morsi and demanded he go on trial after deadly clashes left the Islamist leader scrambling to contain fallout from footage of police brutality.

The opposition National Salvation Front demanded Morsi be prosecuted for "killings and torture" as it urged Egyptians to stage peaceful protests.

Egypt's President Mohamed Morsi vowed security forces will "act with utmost decisiveness" to protect state buildings, as protesters clashed with police outside the presidential palace on Friday.

The presidency, in a statement posted on his Facebook page, also said it would hold "politically accountable" opposition groups behind the violence.

Several thousand Egyptians marched in Port Said on Friday's first anniversary of a deadly football riot in protest against the Islamist government, unfazed by a heavy troop presence after bloody clashes.

"The people of Port Said want independence!" the crowd chanted as they marched past the governorate building in a tense atmosphere.

Egyptian security used water cannon and fired shots into the air as protesters threw petrol bombs and stones into the grounds of the presidential palace in Cairo on Friday, an AFP correspondent said.

The clashes came amid rallies in several cities against Islamist President Mohammed Morsi following unrest that killed 56 people, mostly in Port Said, after 21 residents were sentenced to death over a football-related riot in 2012.

Thousands of Egyptians took to the streets on Friday in a show of opposition to Islamist President Mohamed Morsi and his Muslim Brotherhood after a wave of deadly unrest swept the country.

Protesters braved rare Cairo rainfall to march to Tahrir Square and the presidential palace, chanting "Freedom!" and "Morsi is illegitimate!"

Twitter's unmatched platform for public opinion is emboldening Gulf Arabs to exchange views on delicate issues in the deeply conservative region, despite strict censorship that controls old media.

The authorities have been attempting to limit the damage by handing out jail terms to some whose tweets have been deemed offensive in the Muslim states, including in Bahrain, Kuwait and Saudi Arabia.

Egyptian authorities on Thursday detained a member of the Black Bloc militant group suspected of planning to carry out an Israeli-directed sabotage plan, the official MENA news agency said.

One person "belonging to the Black Bloc organization was arrested inside a building overlooking Tahrir Square carrying Israeli plans to target petrol companies and vital installations, maps of these places and instructions on setting fire to some places," MENA reported.