Egyptian police have fought with thousands of demonstrators who defied a government ban on to protest against President Hosni Mubarak's 30-year-old rule.
Police fired rubber bullets and tear gas and before arresting hundreds of the demonstrators.
Protestors burned tyres and hurled stones at police as groups gathered at different parts of the capital Cairo.
It has been reported that at least one protestor and one policeman have been killed in the city.
Demonstrators also clashed in other cities around Egypt. In Suez, east of Cairo, protestors set fire to a government building.
The scenes follow the overthrow two weeks ago of another long-serving Arab leader, Tunisian leader Zine al-Abidine Ben Ali, in a popular revolt.
Activists had called on people to rally again after a 'Day of Wrath' yesterday of anti-government rallies across Egypt in which three protestors and one policeman were killed.
The demonstrators have complained of poverty, unemployment, corruption and repression and, inspired by the Tunisian revolt, are demanding that Mr Mubarak step down.
'The people want the regime to fall,' protestors chanted.
Security forces have arrested about 500 demonstrators over the two days, an Interior Ministry source said.
Witnesses said officers, some in civilian clothes, hauled away people and bundled them into unmarked vans. Some were beaten with batons.
Police fired shots into the air near the central Cairo court complex, witnesses said.
In another area, they drove riot trucks into a crowd of about 3,000 people to force them to disperse.
A protestor in the centre of Cairo told Reuters news agency: 'The main tactic now is we turn up suddenly and quickly without a warning or an announcement. That way we gain ground.'
Social networking sites, such as Twitter and Facebook, have been a key means of communications for the protestors.
Egyptians complained that Facebook and Twitter were subsequently blocked, but many accessed them via proxies. The government has denied any role in blocking the sites.