CAIRO — Supporters of Egyptian President Hosni Mubarak charged into Cairo's central square on horses and camels brandishing whips while others rained firebombs from rooftops in what appeared to be an orchestrated assault against protesters trying to topple Egypt's leader of 30 years. Three people died and over 600 were injured.The protesters accused Mubarak's regime of unleashing a force of paid thugs and plainclothes police to crush their unprecedented 9-day-old movement, a day after the 82-year-old president refused to step down. They showed off police ID badges they said were wrested from their attackers. Some government workers said their employers ordered them into the streets.RELATED:Rattling the Cage: Enemy of Arab democracy – that’s usUN sources suggest Amr Moussa as Mubarak successorAshkenazi: Unrest could change our security reality"If any of the violence is instigated by the government, it should stop immediately," said White House Press Secretary Robert Gibbs.The clashes marked a dangerous new phase in Egypt's upheaval: the first significant violence between government supporters and opponents. The crisis took a sharp turn for the worse almost immediately after Mubarak rejected the calls for him to give up power or leave the country, stubbornly proclaiming he would die on Egyptian soil.Mubarak's supporters turned up on the streets Wednesday in significant numbers for the first time. Some were hostile to journalists and foreigners. Two Associated Press correspondents and several other journalists were roughed up in Cairo. State TV had reported that foreigners were caught distributing anti-Mubarak leaflets, apparently trying to depict the movement as foreign-fueled.