Egyptian security forces responded with tear gas and water cannons to disperse protesters marching on downtown Cairo.
Egyptian law bans public demonstrations without a permit and Interior Minister Habib el-Adly said there were orders to "arrest any persons expressing their views illegally," al-Jazeera reports.
Protesters who spoke to al-Jazeera correspondents said state security forces were on edge because of the large number of people attending the demonstrations Tuesday.
Following the Tunisian revolution inspired by a protest suicide in December, demonstrators Tuesday chanted slogans calling for the ouster of Egyptian President Hosni Mubarak.
The Tunisian president fled the country to Saudi Arabia after a December suicide sparked a revolution that brought down the government. Egyptian groups called for similar protests in the United States and Great Britain.
Organizers using the social networking Web site Facebook said the Tuesday demonstrations against repression and high unemployment rates in Egypt were "the beginning of the end."
The Muslim Brotherhood, Egypt's main opposition group, wasn't behind the uprising according to al-Jazeera, though its members were taking part in the protests.
The protests Tuesday were described as the largest Egypt has experienced in several years.