Antigovernment protesters, police clash in Cairo

The protests, at least partly inspired by the toppling of the authoritarian government in Tunisia, began small but grew all day, with protesters occupying one of Cairo’s central squares. Security forces, which normally prevent major public displays of dissent, initially struggled to suppress the demonstrations.

But early this morning, firing rubber bullets, tear gas, and concussion grenades, the police finally drove groups of demonstrators from the square, as the sit-in was transformed into a spreading battle involving thousands of people and little restraint. Plainclothes officers beat several demonstrators, and protesters flipped over a police car and set it on fire.

Protests also flared in Alexandria, Suez, Mansura, and Beni Suef. There were reports of three deaths and many injuries.

Photographers in Alexandria documented people tearing up a large portrait of Mubarak. A video posted on the Internet of demonstrations in Mahalla el-Kubra showed the same, while a crowd snapped cellphone photos and cheered. The acts — rare, and bold here — underscored the anger coursing through the protests and the challenge they might pose to the aging and ailing Egyptian leader.

Several observers said the protests represented the largest display of popular dissatisfaction with the government in recent memory, perhaps since 1977, when people across Egypt protested the elimination of subsidies for food and other basic goods.

It was not clear whether the size and intensity of the demonstrations — which seemed to shock even the protesters — would or could be sustained.

The government quickly placed blame for the protests on the country’s largest opposition movement, the Muslim Brotherhood, which is tolerated but officially banned. In a statement, the Interior Ministry said the protests were the work of “instigators’’ led by the Muslim Brotherhood, while the Islamic movement declared that it had little to do with them.

The reality that emerged from interviews with protesters — many of whom said they were independents — was more complicated and reflected one of the Egyptian government’s deepest fears: that the opposition to Mubarak’s rule now spreads across ideological lines and includes many people angered by corruption and economic hardship as well as secular and Islamist opponents. That broad base of support could make it harder for the government to co-opt or crush those demanding change.

“The big, grand ideological narratives were not seen today,’’ said Amr Hamzawy, research director of the Carnegie Middle East Center. “This was not about ‘Islam is the solution’ or anything else.’’

Security officials said a soldier in Cairo, along with two protesters in Suez, were killed in circumstances that were not immediately clear. Scores of demonstrators and more than a dozen soldiers were injured in the Cairo clashes, which lasted hours and included bouts of rock-throwing by both protesters and the police.

There were mixed signals about how the authorities planned to handle the unrest. In contrast with other recent political demonstrations in Cairo, thousands of security officers seemed content at times to contain rather than engage the protesters — especially when it became clear that the demonstrators would not retreat from Tahrir Square. In a statement, the Interior Ministry said its policy had been “securing and not confronting these gatherings.’’

But there were signs of other containment tactics: Several times, cellphone networks appeared to be blocked or otherwise unavailable for people calling from Tahrir — or Liberation — Square. Many had trouble accessing Twitter, the social networking tool that helped spread news of the protests. Twitter confirmed that its site had been blocked in Egypt, Reuters reported. For much of the day, state television made no mention of the demonstrations.

By early this morning, the police appeared determined to clear protesters from the streets, leading to more clashes.

On a bridge, drivers stopped and some joined the protesters, chanting, “The people want the downfall of the regime.’’ Below the bridge, owners of the feluccas that cruise the Nile with tourists unmoored and set sail.