"We believe that 1,000 people -- maybe more -- were detained yesterday and today," said Khaled Ali, an attorney for a Cairo rights group, the Egyptian Demonstrators Defense Front.
The newspaper said most of the arrests occurred in Cairo, Alexandria, Mansoura and Suez. Ali claimed the Ministry of Interior was holding the detainees at two camps used to train Egyptian security forces and were being prevented from contacting their families or lawyers.
After a fourth person died of protest-related wounds, Egyptian authorities Wednesday banned demonstrations in the country and warned violators would be arrested.
"No provocative moves or protest gatherings or marches or demonstrations will be allowed. Legal measures will be taken against anyone and they will be transferred to the prosecution," a ministry statement said.
Gharib Abdellatif, 45, died in a hospital in Suez, east of Cairo, the fourth protester killed during Tunisia-inspired protests against the government that rocked Egypt Tuesday, Egyptian newspaper al-Masry al-Youm said. Two other Egyptian protesters were killed by rubber bullets and a police officer died after being hit in the head by a stone, the newspaper said.
Cairo Health Director Nibal Abdel Kader said 124 people were injured and warned the number was expected to rise as further demonstrations are expected, Egyptian newspaper al-Ahram said.
Police arrested 200 demonstrators who participated in Tuesday's clashes calling for an end to Mubarak's rule, Arabic TV station al-Arabiya reported.
Tuesday night, Egyptian opposition groups held a news conference demanding Mubarak not enter the upcoming presidential elections, al-Masry al-Youm said.
The groups also demanded his son, Gamal Mubarak, who heads the ruling National Democratic Party's secretariat, not be nominated as a presidential candidate.
"Today's demonstrations will be a turning point in the history of the Egyptian people," said Abdel Gelil Moustafa, coordinator of the National Association for Change.
Protesters converged in Cairo's Tahrir Square, the Egyptian capital's main interchange, in the pre-dawn hours Wednesday but dispersed -- promising to return -- after police fired rubber bullets, tear gas and concussion grenades, witnesses said. Protests also occurred in Alexandria, Suez, Mansura and Beni Suef, The New York Times said.
The government blamed the protests seeking to end Mubarak's 30-year rule on the country's largest opposition movement, the Society of the Muslim Brother, an officially banned Islamic political group. The group said it did not participate in the protests, but some of its members were among the Cairo demonstrators, the Times said.
The protests marked the greatest upsurge of Arab world anger so far since the Tunisian protests that culminated Jan. 14 with the ouster of President Zine el-Abidine Ben Ali after 23 years in power.