Egypt's highest judicial authority criticised the decree by Mursi that makes his decisions immune from judicial oversight.
The new constitutional declaration is "an unprecedented attack on the independence of the judiciary and its rulings," the Supreme Judicial Council said in a statement.
A group of opposition activists spent the night in the iconic Tahrir Square, erecting some 30 tents. But when more demonstrators attempted to join them this morning, police fired tear gas canisters, forcing them to retreat.
Nearly two years after popular unrest spurred former Egyptian President Hosni Mubarak's fall, people have taken to Egypt's streets in past days to call for revolution again, this time for the ouster of "new pharaoh" Mursi.
On Thursday, Mursi announced that courts could not overturn any decree or law he has issued since taking office in June and, beyond that, in the six months until a new constitution is finalised.
He also fired Egypt's general prosecutor, who has been criticised for the insufficient prosecutions of those suspected in demonstrators' deaths in 2011.
Tents dotted Cairo's iconic Tahrir Square, just as they did during the 2011 uprising, and clashes between protesters and police were reported yesterday and today in the capital, the port city of Alexandria and elsewhere in the country.
Thousands of his supporters and opponents yesterday took to streets to stage rival rallies across Egypt, leading to sporadic violence and burning down of offices belonging to the ruling Muslim Brotherhood.
Following Mursi's decision to seize more power for himself through a decree, the US has expressed concern for Egyptians and for the International communities.
Minor clashes also broke out when demonstrators on Mohamed Mahmoud Street near Tahrir Square threw rocks at security forces, who fired back with tear gas.
