Egyptian President Mursi has refused to take back a decree that granted him sweeping powers, and the opposition is taking to the street in protest.
Thousands of people protested on Cairo's Tahrir Square on Saturday, following the acquittal of Hosni Mubarak, who had appealed a life-prison sentence for the killing of anti-regime protesters in 2011.
Police in Egypt have defused two bombs at Cairo International Airport, according to security officials. Another bomb went off in the center of Egypt's capital.
At least one policeman has been wounded in Cairo on the anniversary of the country's revolution against Hosni Mubarak. Four years on, Egyptians on both sides face tough restrictions when trying to stage protests.
About 2,000 Islamists have rallied in Cairo. In Egypt’s coastal city of Alexandria police fired tear gas to disperse Muslim Brotherhood supporters when they clashed with counterprotesters, a security official said.