Dusk is falling in Egypt but demonstrators remain on the streets in Cairo and Alexandria, in defiance of the government's nighttime curfew.
The Associated Press says there are new reports of looting as well as several fires in the Cairo area, including one at a major supermarket in a suburb of the capital.
Meanwhile, protesters who oppose President Hosni Mubarak's decision to remain in office until the end of his term have pledged to launch mass demonstrations Friday as they press for the president's immediate departure.
Earlier Thursday, Egyptian soldiers took positions between pro- and anti-government protesters in Cairo, where gunfire had erupted earlier in the day. Several tanks were stationed near Cairo's Tahrir Square as thousands of anti-government protesters gathered there and built barricades.
One of the tanks stood on a highway overpass, where earlier Thursday, supporters of President Mubarak had been throwing rocks at anti-government protesters below.
Also Thursday, Prime Minister Ahmed Shafiq apologized for violent clashes that broke out Wednesday when supporters of Mr. Mubarak surged into Tahrir Square and faced off against opposition demonstrators. He called the incident a "disaster" and said it would not happen again.
In his news conference carried on state television, Mr. Shafiq also said his government did not have enough police to adequately control security during the clashes.
State news reports say Vice President Omar Suleiman has called on security forces to release youth detained in the protests who were not involved in violence. State news reports also quote Suleiman as saying President Mubarak's son, Gamal, will not run for president.
After Wednesday's violence, doctors set up a makeshift clinic in a mosque near Tahrir Square to help the more than 640 injured. There were reports of several deaths.
Anti-government protesters accused Mr. Mubarak's government of unleashing paid vandals and undercover police Wednesday to crush their uprising. The Interior Ministry denied the charge.
The 82-year-old Mr. Mubarak announced late Tuesday he will not seek reelection in September, but he vowed to serve out his term until then. He spoke after an estimated 250,000 people flooded Tahrir Square to demand his resignation. Anti-Mubarak protesters also rallied in other major Egyptian cities.