Egyptian riot police firing tear gas and rubber bullets stormed into Cairo's Tahrir Square Saturday to dismantle a protest tent camp, setting off clashes that injured at least 507 people and raising tensions days before the first elections since Hosni Mubarak's ouster.
The scenes of protesters fighting with black-clad police forces were reminiscent of the 18-day uprising that forced an end to Mubarak's rule in February. Hundreds of protesters fought back, hurling stones and setting an armored police vehicle ablaze.
The violence raised fears of new unrest surrounding the parliamentary elections that are due to begin in nine days' time. Public anger has risen over the slow pace of reforms and apparent attempts by Egypt's ruling generals to retain power over a future civilian government.
Witnesses said the clashes began when riot police dismantled a small tent camp set up to commemorate the hundreds of protesters killed in the uprising and attacked around 200 peaceful demonstrators who had camped in the square overnight in an attempt to restart a long-term sit-in there.
"Violence breeds violence," said Sahar Abdel-Mohsen, an engineer who joined in the protest after a call went out on Twitter urging people to come to Tahrir to defend against the police attacks. "We are tired of this and we are not leaving the square."
Police fired rubber bullets, tear gas and beat protesters with batons, clearing the square at one point and pushing the fighting into surrounding side streets of downtown Cairo. State TV, quoting the Health Ministry, reported that 507 people were injured, including 19 policemen.
Abdel-Mohsen said a friend was wounded by a rubber bullet that struck his head and that she saw another protester wounded by a pellet in his neck.
Crowds swarmed an armored police truck, rocking it back and forth and setting it ablaze. Black smoke rose over the crowd.
After nightfall, protesters swarmed back into the square in the thousands, setting tires ablaze in the street and filling the area with an acrid, black smoke screen. Police appeared to retreat to surrounding areas, leaving protesters free to retake and barricade themselves inside the square. The air was still thick with stinging tear gas.
Prime Minister Essam Sharaf urged the protesters to clear the square.
Saturday's confrontation was one of the few since the uprising to involve police forces, which have largely stayed in the background while the military takes charge of security. There was no military presence in and around the square on Saturday. The black-clad police were a hated symbol of Mubarak's regime.
"The people want to topple the regime," shouted enraged crowds, reviving the chant from the early days of the uprising. Crowds also screamed: "Riot police are thugs and thieves" and "Down with the Marshal," referring to Field Marshal Hussein Tantawi, Egypt's military ruler.
Human rights activists accused police of using excessive force.
One prominent activist, Malek Mostafa, lost his right eye from a rubber bullet, said Ghada Shahbender, a member of the Egyptian Organization for Human Rights. At least four protesters were injured in the eyes as a result of what Shahbender said were orders to target protesters' heads.
"It is a crime," she said. "They were shooting rubber bullets directly at the heads. ... I heard an officer ordering his soldiers to aim for the head."
Police arrested 18 people, state TV reported, describing the protesters as rioters.
A day earlier, tens of thousands of Islamists and young activists had massed in Tahrir Square to protest Egypt's ruling military council, which took control of the country after Mubarak's ouster and has been harshly criticized for its oversight of the bumpy transition period.
Friday's crowd, the largest in months, was mobilized by the Muslim Brotherhood and focused its anger on a document drafted by the military that spells out guiding principles for a new constitution.
Under those guidelines, the military and its budget would be shielded from civilian oversight. An early version of it also said the military would appoint 80 members of the 100-person constitutional committee - a move that would vastly diminish the new parliament's role.
Groups across the political spectrum rejected the document, calling it an attempt by the military to perpetuate its rule past the post-Mubarak transition.