Gunfire broke out Saturday as Egyptian security forces tried to get Muslim Brotherhood partisans to leave a mosque where they took refuge overnight.
Government forces surrounded the mosque as small clusters of people left from time to time. The Interior Ministry says more than a thousand people were detained overnight across the country, and that Friday's death toll stands at 173.
Gunshots rang out, at times heavily, as security forces fired on the minaret of the al-Fatah Mosque, where Brotherhood supporters have been holed up since Friday. Earlier, scuffles broke out between police and army troops ringing the main entrance.
Elizabeth Arrott reports from Cairo
Al Jazeera Television, which tends to support the Brotherhood, showed images of a cluster of veiled women trying to stop police from approaching the building. The TV's reports in Arabic urged Egyptians to come to the mosque to “defend those inside” - believed to include several top Brotherhood leaders.
Arab media reported that a son of the group's spiritual leader, Mohamed Badie, was killed in clashes near the mosque Friday. Al-Ahram Online reported that Islamist Mohamed Zawahiri, brother of al-Qaida leader Ayman Zawahiri, was arrested by police Saturday.
Egypt's interim prime minister, Hazem le-Beblawi, said the new government will work "until its last breath" to find a democratic solution to the crisis - but not with those who use violence:
He says, "Our job is to move to a democratic system with a consensual constitution, with free elections. But there can be no reconciliation with those who have fired on the state."
A spokesman for Egypt's interim government told reporters Saturday that a handful of foreigners, including Syrians, Pakistanis and a Palestinian, were arrested, and quantities of ammunition, molotov cocktails and assorted weapons were confiscated.
The spokesman insisted that the government would continue to “use an iron fist against acts of violence,” and said that violence included attacks on 12 churches, two prisons, numerous shops, the Finance Ministry, the library in Alexandria and various government buildings.
He says he cannot call what took place a “peaceful protest,” but that police are trying to use maximum restraint and negotiate with protesters, to avoid bloodshed.
Muslim Brotherhood officials say they are planning more protests later Saturday, but gave no details. The Islamist group said earlier that its “Friday of Rage” protests will continue for a full week.