Egypt's military deployed on the streets of Cairo to enforce a nighttime curfew as the sun set Friday on a day of rioting and chaos that amounted to the biggest challenge ever to authoritarian President Hosni Mubarak's 30-year regime. Flames rose up across a number of cities from burning tires and police cars. Even the ruling party headquarters in Cairo was ablaze in the outpouring of rage, bitterness and utter frustration with a regime seen as corrupt, heavy-handed and neglectful of grinding poverty that afflicts nearly half of the 80 million Egyptians. After nightfall, some of the protesters defied the curfew and were praying on the streets of Cairo. In one of many astonishing scenes Friday, thousands of anti-government protesters wielding rocks, glass and sticks chased hundreds of riot police away from the main square in downtown Cairo and several of the policemen stripped off their uniforms and badges and joined the demonstrators. Protestors attempt to get into Tahrir Square. Egyptian anti-riot policemen use water canons against protesters in Cairo. Riot police face protestors on the Kasr Al Nile Bridge.