A protester and a police officer were killed in central Cairo as anti-government demonstrators pelted security forces with rocks and firebombs for a second day, according to witnesses.
Activists had called on people to rally again on Wednesday after a "Day of Wrath" the previous day had seen thousands of people take to the streets across Egypt to complain of poverty, unemployment, corruption and repression.
A total of six people, four protesters and two policemen, have been killed so far in the largely unprecedented mass anger at the 30-year rule of Hosni Mubarak, the Egyptian president.
"The people want the regime to fall," protesters chanted.
Hillary Clinton, the US secretary of state, has said that the protests represent an opportunity for the administration to implement "political, economic and social reforms to respond to the legitimate needs and interests of the Egyptian people".
In the unusually blunt remarks regarding the longtime US ally, Clinton also said that the Mubarak government should not prevent peaceful protests or block social networking sites such as Twitter or Facebook, which have helped Egyptians plan and spread news about the unrest.