Protesters clash with police in downtown Cairo on Tuesday, in unprecedented protests inspired by the revolt that brought down Tunisia's president. (Mohamed Abd El-Ghany/Reuters)

Thousands of anti-government protesters clashed with riot police Tuesday in the centre of Cairo to demand the end of Hosni Mubarak's nearly 30 years in power.

Three people were killed in confrontations around the country.

After a day of violence, thousands of demonstrators stood their ground in downtown Cairo's vast Tahrir Square, steps away from parliament and other government buildings. They promised to camp out overnight, setting the stage for an even more dramatic confrontation.

Police use a water cannon against anti-government protesters in downtown Cairo. (Amr Abdallah Dalsh/Reuters)Throughout the day, police blasted crowds with water cannons and set upon them with batons and acrid clouds of tear gas in an attempt to clear demonstrators crying out "Down with Mubarak" and demanding an end to Egypt's grinding poverty, corruption, unemployment and police abuses.

Tuesday's demonstration, the largest Egypt has seen for years, began peacefully, with police showing unusual restraint in what appeared to be a calculated strategy by the government to avoid further sullying the image of a security apparatus widely criticized as corrupt and violent.

With discontent growing over economic woes, and the toppling of Tunisia's president still resonating in the region, Egypt's government — which normally responds with swift retribution to any dissent — needed to tread carefully.

Protests turned violent

But as crowds filled Tahrir Square — waving Egyptian and Tunisian flags and adopting the same protest chants that rang out in the streets of Tunis — security personnel changed tactics and the protest turned violent. Around 10,000 protesters packed the square, the Interior Ministry said.

The sight of officers beating demonstrators had particular resonance because Tuesday was also a national holiday honouring the much-feared police.

A policeman was hit in the head with a rock during the protest in Cairo and died later in the hospital, an Interior Ministry official said.

In another demonstration in the city of Suez, two protesters were killed, he said. One of them had respiratory problems and died as a result of tear gas inhalation; the other was killed by a rock.

The official spoke on condition of anonymity because he was not authorized to release information to journalists.

In Egypt, discontent with life in the autocratic, police state has simmered under the surface for years. It is the example of Tunisia, though, that appeared to be enough to push many young Egyptians into the streets for the first time.

"This is the first time I am protesting, but we have been a cowardly nation. We have to finally say no," said 24-year-old Ismail Syed, a hotel worker who struggles to live on a salary of roughly $50 a month.

Demonstrators attacked a water cannon truck, opening the driver's door and ordering the man out of the vehicle. Some hurled rocks and dragged metal barricades. Officers beat back protesters with batons as they tried to break cordons to join the main group of demonstrators downtown.

Protesters emerged stumbling from white clouds of tear gas, coughing and covering their faces with scarves.

Some had blood streaming down their faces. One man fainted. Police dragged some away and beat a journalist, smashing her glasses and seizing her camera.

Crowds also marched to the headquarters of Mubarak's National Democratic Party, shouting, "Here are the thieves."

After remaining silent throughout the day, Egypt's government on Tuesday night called for an end to the protests. The Interior Ministry, which controls the security forces, said authorities wanted to allow the protesters the chance to express their opinions and accused the crowds of "insisting on provocation."

"Some threw rocks at police ... and others carried out acts of rioting and damage to state institutions," the government said.

Twitter blocked

Twitter Inc. confirmed via a tweet that its service had been blocked in Egypt.

"We believe that the open exchange of info & views benefits societies & helps govts better connect w/ their people," the company said.

Social media tools, such as Twitter and Facebook, have been used extensively to rally support for the protesters.

Egyptian organizers had been using Twitter to send out instructions to people on where to gather, until the government blocked the service late Tuesday afternoon local time.

Anti-government protesters fill Cairo's Tahrir Square on Tuesday. (Submitted photo) With files from CBC News