At least three people have been killed during a day of rare anti-government protests in Egypt, reports say.
In Cairo, where the biggest rallies were held, state TV said a policeman had died in clashes. Two protesters died in Suez, doctors there said.
Thousands joined the protests after an internet campaign inspired by the uprising in Tunisia.
In Cairo, police used tear gas and water cannon in an attempt to disperse the crowds.
Activists had called for a "day of revolt" in a web message. Protests are uncommon in Egypt, which President Hosni Mubarak has ruled since 1981, tolerating little dissent.
US Secretary of State Hillary Clinton said her administration supported "the fundamental right of expression and assembly" and urged all parties "to exercise restraint".
She added that Washington believed the Egyptian government was "stable" and "looking for ways to respond to the legitimate needs and interests of the Egyptian people".
The events in Cairo were co-ordinated on aFacebook page - tens of thousands of supporters clicked on the page to say they would take part.
Reports said the social networking site Twitter had been blocked in Egypt and that mobile phone networks in the Cairo area were down.
The Swedish-based website Bambuser, which streams video from mobile phones, said it had been blocked in Egypt. On its blog, it accused Egyptian officials of trying to control the news agenda.
The BBC's Jon Leyne in Cairo said rallies had been held in several parts of the capital, and the turnout had been more than the organisers could have hoped.
Police were taken aback by the anger of the crowd and let protesters make their way to the parliament building, he says.
There police regrouped in full riot gear with tear gas and water cannon and temporarily drove the crowd back. However, protesters threw stones and stood their ground, pushing the police back until they were on the run.
Protests also broke out in other areas, including the eastern city of Ismailiya and the northern port city of Alexandria.
In Alexandria, witnesses said thousands joined the protests, some chanting: "Revolution, revolution, like a volcano, against Mubarak the coward."
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