Up to 200,000 protesters have participated in a rally in Cairo's Tahrir Square to condemn the autocratic powers recently assumed by Egyptian president Mohammed Mursi.
The demonstrators chanted slogans such as "the people want the fall of the regime" and "erhal! erhal! [Leave, leave]", which were also shouted at former President Hosni Mubarak before he was overthrown last January.
Referring to the uprising which culminated in Mubarak's removal, protesters held banners which read "The Muslim Brotherhood stole the revolution" and "The Muslim Brotherhood are liars."
However the Brotherhood has maintained its support for Mursi's latest decree, which grants him a range of powers including immunuty over the judiciary, and facilitates the retrial of Mubarak supporters acquitted of violence following last January's revolution.
"On January 25, united Egyptians [Islamists, liberals and leftists] revolted against autocracy, supported by millions across the country. Today is politics," the Brotherhood tweeted.
"When ordinary Egyptians across the nation see pro-Mubarak [elements] protesting in Tahrir along with Islamists' rivals, they know this isn't January 25. The opposition thinks the significance of today is of Tahrir protesters; they should brace for millions in support of the elected president."
Initially, the Islamist group planned to hold a rally supporting the decree but this was later called off due to fears that it would turn violent.
"If the decree isn't undone, we will demand that Mursi himself leave. Then we can have new presidential elections. We plan to remain in [Tahrir] square until Mursi backtracks on his constitutional decree," Khaled Metwali, a member of the left-wing Democratic Revolutionary Coalition told Egypt's al-Ahram online.
Three people have so far been killed and dozens of others injured during violent clashes across the capital following the announcement of Mursi's decree last week.