Opposition groups in Egypt are calling for mass protests after President Mohammed Mursi passed a decree giving him sweeping powers.
Leading opposition figures have denounced it, accusing the president of appointing himself as Egypt's "new pharaoh".
The president said his decree was aimed at "cleansing state institutions" and "destroying the infrastructure of the old regime".
The decree states that the president's decrees, laws and decisions cannot be overturned by any authority - including the judiciary. It says no court can dissolve the constituent assembly, which is drawing up a new constitution, the BBC reports.
Mr Mursi has sacked chief prosecutor Abdel Maguid Mahmoud and ordered the retrial of people accused of attacking protesters during an uprising in 2011 which toppled President Hosni Mubarak.
The action could lead to a retrial of Mubarak, who is serving a life sentence.
In a news conference on Thursday, Sameh Ashour, head of the lawyers syndicate, and key opposition figures Mohamed ElBaradei and Amr Moussa accused Mr Mursi of "monopolising all three branches of government" and overseeing "the total execution of the independence of the judiciary".
"We are calling on all Egyptians to protest in all of Egypt's squares on Friday," they said.
But Mr Mursi's supporters say the move will protect Egypt's revolution. Thousands celebrated the decree in front of the the High Court in Cairo on Thursday.
Mahmoud Ghozlan, spokesman for Mr Mursi's Muslim Brotherhood party, described it as "revolutionary and popular."
Mr Mursi's declaration also gives the 100-member constituent assembly an additional two months to draft a new constitution to replace the one suspended after Mr Mubarak was overthrown. A re-write was originally meant to be finished by December. The finished document is to be put to a referendum.