Egypt's most senior judges have condemned President Mohamed Morsi for granting himself sweeping new powers which they say amount to an "unprecedented assault" on the independence of the judiciary.

The supreme judicial council said work would be suspended in all courts and prosecution offices until the decree passed by the president earlier this week was reversed.

The announcement by the top judges, most of whom were appointed by former President Hosni Mubarak, came after tens of thousands of Egyptians took to the streets on Friday to protest against Morsi's decree.

The judicial body had previously urged the president on Thursday to "distance this decree from everything that violates the judicial authority".

The new edicts give the president near-absolute power and immunity from appeals in courts for any decisions or laws he declares until a new constitution and parliament is in place.

Opponents of the decree have called for a large-scale demonstration on Tuesday. In a second day of protests on the streets of Cairo on Saturday, activists threw rocks at riot police, while a few dozen people manned makeshift barricades to keep traffic out of Tahrir Square.

The decree has polarised opinion between the newly empowered Islamists, represented by Morsi's Muslim Brotherhood, and their opponents. Leftwing and liberal parties have called for an open-ended sit-in aimed at "toppling" the decree.

"We are facing a historic moment in which we either complete our revolution or we abandon it to become prey for a group that has put its narrow party interests above the national interest," the liberal Constitution party said in a statement.

Anti-Morsi demonstrators, who accuse the president of having launched a "constitutional coup" on Thursday, were reported to have set fire to the offices of the Muslim Brotherhood's Freedom and Justice party, to which Morsi belongs, in the Suez Canal cities of Suez and Port Said on Friday.

Clashes also erupted on Friday between the two sides in the Mediterranean city of Alexandria, the southern city of Assiut and Giza, prompting Essam el-Erian, a leading figure in the FJP, to condemn the attacks as "acts of thuggery hiding behind political forces". While in Cairo, the two opposing camps gathered in large rival rallies. In a packed Tahrir Square, youths opposed to the decree fought intermittent battles with police firing volleys of teargas outside the French Lycée and American University. Morsi's Muslim Brotherhood meanwhile bussed in supporters from across the country to hear him address a rally outside the presidential palace in Heliopolis.

Morsi's decree orders the retrial of former president Hosni Mubarak, officials and security force members accused of killings during the country's revolution. Controversially, it also exempts all of Morsi's decisions from legal challenge until a new parliament is elected, as well as offering the same protection to the Islamist-dominated constituent assembly, which is drawing up the country's new constitution.

Morsi's aides said the presidential decree was to speed up a protracted democratic transition that has been hindered by legal obstacles. Morsi's rivals, however, were quick to condemn him as a new autocratic pharaoh who wanted to impose his Islamist vision on Egypt.

Morsi made the move in a week in which he had been buoyed by accolades from around the world for mediating a truce between Hamas and Israel. "I am for all Egyptians. I will not be biased against any son of Egypt," Morsi said on a stage outside the presidential palace, adding that he was working for social and economic stability and the rotation of power. "Opposition in Egypt does not worry me, but it has to be real and strong," he said in response to his critics.