Tahrir, or Liberation, Square, where protesters gathered for a ninth day, turned into a battleground as Mubarak supporters flooded the area, chanting, "He is not leaving."
As clashes continued late into the night, Egypt's State television asked protesters to leave Tahrir Square. Egyptian security stormed rooms at a hotel nearby, according to one reporter, and took down cameras and feeding equipment from its balconies.
Fiery Molotov cocktails -- gasoline bombs -- could be seen thrown into the crowd, although it was not clear which side was launching them. Water cannons were also fired at protesters. There were multiple reports of petrol bombs causing fires inside the grounds of the Egyptian Museum.
The White House condemned the riots but stopped short of condemning the government for the violence. President Obama "found the images outrageous and deplorable," White House Press Secreatry Robert Gibbs said.
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Each road going into Tahrir Square seemed to have its own drama unfolding. A human chain of anti-government protesters was seen on one side trying to block pro-government supporters from entering. On the next road, a thick mob pushed into what appeared to be street fighting.
The two sides skirmished with fists, rocks and bottles as helicopters flew overhead. Riders were pulled from camels and horses, and injured demonstrators, many with bloodied faces, were carried away. Warning gunshots were fired and tanks were placed to keep the two sides separated, but neither move by the army had any effect.
Protesters earlier were seen rushing towards pro-Mubarak supporters to push them out of Tahrir Square, which has in recent days, become a symbol of liberation for protesters. From ABC News' vantage point on a roof of a building in Tahrir Square, the military was blocking about 2,000 pro-Mubarak protesters from entering.
Egypt's health minister said that three people died in the chaos and as many as 600 were injured, but anti-government activists said those numbers were low.
Thousands of pro-Mubarak demonstrators converged on the city's center earlier today and clashed with the anti-Mubarak protesters who have occupied the city's main square for more than a week, demanding the president step down immediately. Pro-Mubarak demonstrators also lashed out at the foreign press, particularly Al Jazeera, who they blame for stirring the uprising.
An angry mob surrounded and chased the ABC News crew in a car today, shouting that they hate America. They kicked in the car doors and broke the windshield as we drove away.
Mubarak's supporters came out a day after the 82-year-old president announced that he will not run for reelection, but insisted that he would stay in office until elections are held in September.
The mood in Tahrir Square turned from jubilation on Tuesday to tension today, as demonstrators were sprayed with tear gas.