Riot police detain supporters of ousted Egyptian President Mohamed Mursi and the Muslim Brotherhood at Talaat Harb Square, in Cairo January 25, 2015 (Photo: Reuters)

Armoured vehicles and barbed wire block an entrance to Tahrir Square during the 4th anniversary of the January 2011 uprising, in Cairo January 25, 2015 (Photo: Reuters)

Egyptian security officials inspect the site of a bomb blast near the Alf Maskan district of Cairo, January 25, 2015 (Photo: Reuters)

Supporters of an anti-Muslim Brotherhood group hit a supporter of ousted Egyptian President Mohamed Mursi and the Muslim Brotherhood at Talaat Harb Square in Cairo, January 25, 2015 (Photo: Reuters)

Army soldiers in military vehicles move to take up positions during the fourth anniversary of the 2011 uprising that toppled autocrat Hosni Mubarak in Cairo, January 25, 2015 (Photo: Reuters)

Egyptians march during the funeral procession of Shaimaa el-Sabagh, a 32-year-old mother of one from the Mediterranean port city of Alexandria, who was shot Saturday in downtown Cairo while taking part in a gathering commemorating the nearly 900 protesters killed in the revolution, in Alexandria, Egypt, Sunday, Jan. 25, 2015 (Photo: AP)

An Egyptian is arrested by plainclothes police in downtown Cairo, Egypt, Sunday, Jan. 25, 2015 (Photo: AP)

An Egyptian is arrested by plainclothes police in downtown Cairo, Egypt, Sunday, Jan. 25, 2015 (Photo: AP)

Protester chant slogans in downtown Cairo, Egypt, Sunday, Jan. 25, 2015 (Photo: AP)

Anti-government protesters run as police arrive during their attempt to walk into Tahrir square in Cairo January 25, 2015 (Photo: Reuters)