Egyptian President Mohamed Morsi has postponed an official visit to France this week, the French presidency said Tuesday, as days of deadly clashes brought his rule to the brink of collapse.

Morsi had been due to meet French President Francois Hollande on Friday to discuss France's military intervention in Mali, which he has criticized.

After winning a tug-of-war with the opposition over Egypt's new constitution in December, Islamist President Mohamed Morsi faces a fresh crisis, one that is hard to pass without him making concessions.

The gravity of the crisis was highlighted Tuesday by Defense Minister General Abdel Fattah al-Sissi, who warned if the current situation persists it could "lead to a collapse of the state".

Egypt's judiciary has ordered the arrest of members of the "Black Bloc", a shadowy group of militants who have appeared among protesters during the latest clashes with police, a judicial source said Tuesday.

Prosecutor General Talaat Ibrahim Abdallah has authorized the arrest "of all people suspected of belonging to the group and ordered that they be brought before the courts," the source said.

A Cairo tribunal on Tuesday upheld death sentences passed on seven Egyptian Coptic Christians in absentia for their involvement in a movie that ridiculed the Prophet Mohammed, a judicial source said.

The accused, including the director of the movie that triggered outrage across the Muslim world when it surfaced last September, are currently living in the United States.

Egypt's military chief warned Tuesday the political crisis sweeping the country could lead to the collapse of the state, as thousands defied curfews and the death toll from days of rioting rose to 52.

"The continuing conflict between political forces and their differences concerning the management of the country could lead to a collapse of the state and threaten future generations," General Abdel Fattah al-Sissi said in a speech to students at a military academy.

Amnesty International on Monday condemned the police's use of deadly force against demonstrators in Egypt, where nearly 50 have been killed in clashes.

"Eyewitness accounts collected by Amnesty International in Egypt point to the unnecessary use of lethal force by security forces during a weekend of clashes with demonstrators," it said.

The White House on Monday condemned the unrest shaking Egypt's fragile peace and called on the country's leaders to make clear that violence is never acceptable.

"We strongly condemn the recent violence that has taken place in various Egyptian cities," said White House spokesman Jay Carney.

Egypt's main opposition bloc on Monday rejected an invitation by President Mohamed Morsi for talks on the violence and political turmoil sweeping the country and instead called for fresh mass demonstrations.

With another person killed in a fifth straight day of clashes in Cairo and the unrest showing no signs of abating, the Islamist-dominated senate ratified a law that would grant the armed forces powers of arrest.

Egypt's cabinet on Monday approved a draft law that would allow President Mohammed Morsi to deploy the armed forces on the streets "to participate with the police in preserving security and protecting vital establishments."

The law, which has to be ratified by the Islamist-dominated upper house of parliament, would apply until after the next legislative elections and be invoked whenever the president deems it necessary, state news agency MENA said.

One person was killed in Cairo Monday as clashes between police and protesters raged into a fifth day, and President Mohammed Morsi scrambled to contain deepening divisions with calls for national dialogue.

The unidentified man was killed by birdshot to the head, a police official told AFP, as demonstrators and police lobbed rocks at each other on a bridge and in an underpass leading to Tahrir Square and tear gas hung heavily in the air.