CAIRO — Egyptian riot police firing tear gas and rubber bullets stormed into Cairo's Tahrir Square Saturday to dismantle a protest tent camp, setting off intense clashes that injured at least 507 people.
The scenes of protesters fighting with black-clad police forces were reminiscent of the 18-day uprising that ousted Hosni Mubarak in February. Hundreds of protesters fought back, hurling stones and setting an armored police vehicle ablaze.
The violence took place just nine days before Egypt's first post-Mubarak parliamentary elections and as public anger rises at 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.
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.
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.
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.
Some of the wounded had blood streaming down their faces and many had to be carried out of the square by fellow protesters to waiting ambulances.
Human rights activists accused police of excessive force.
One prominent activist, Malek Mostafa, lost his right eye from a rubber bullet, said Ghada Shahbandar, a member of the Egyptian Organization for Human Rights.
At least four protesters were injured in the eyes as a result of what Shahbandar 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. Back in February, the military had promised it would return to the country to civilian rule within six months. Now, there is deep uncertainty over the timeline, and presidential elections might not be held until 2013.
Friday's demonstration dispersed peacefully, but several hundred people remained in the square overnight in an attempt to re-establish a semi-permanent presence in the square to pressure the military council.
Violence began in Saturday afternoon, as police moved in to clear them.
The number of protesters swelled to several thousand as news of the fighting spread in the city, and thousands more riot police streamed into Tahrir Square, blocking entrances and clashing with protesters before disappearing after nightfall.
The Interior Ministry, which runs the country's police forces, accused people of trying to escalate tensions ahead of the parliamentary elections, which begin on Nov. 28 and will be held in stages continuing through March.
Activists say they just want to guard the outcome of their revolution.
Unemployed graduate student Nasser Ezzat said he traveled from southern Egypt to Tahrir because he wanted to help finish the revolution that people died for. He came to the square on Friday, leaving behind his a pregnant wife in the city of Sohag.
"I dream of a fairer Egypt for my unborn daughter, one without police harassment and corruption," he said on Saturday.
Crowds also directed their anger at the police, which were the muscle behind Mubarak's heavy handed rule.
"This violence is the same as the old regime," activist Mona Seif said. "Police are telling us they are carrying out orders to beat us until we leave."
Seif is the sister of prominent blogger and activist Alaa Abdel-Fattah, who is in jail after refusing to answer questions over his alleged role in sectarian clashes. He leads a campaign to end the trials of civilians in military courts.
Rights groups estimate that up to 12,000 people have been tried in military courts since Mubarak was ousted.
Associated Press writer Sarah El Deeb contributed to this report.