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.
Armed Egyptian policeman moves into position in front of al-Fath mosque on Ramses Square in Cairo, August 17, 2013.
Policemen stand guard inside a room of the al-Fath mosque when supporters of deposed Egyptian President Mohamed Morsi exchanged gunfire with security forces inside the mosque in Cairo, Aug.t 17, 2013
Anti-Mursi protesters and riot police officers gather outside al-Fath mosque at Ramses Square in Cairo, August 17, 2013.
A police officer takes position during clashes with supporters of deposed Egyptian President Mohamed Morsi inside a room of al-Fath mosque in Cairo, August 17, 2013.
A member of the Muslim Brotherhood and supporter of ousted Egyptian President Mohamed Morsi shouts slogans after he is injured in front Azbkya police station during clashes at Ramses Square, Cairo, August 16, 2013.
Egyptians lay on the ground after being injured during clashes between security forces and supporters of Egypt's ousted President Mohamed Morsi in Ramses Square, Cairo, August 16, 2013.
Supporters of ousted Egyptian President Mohamed Morsi gather in Cairo, August 16, 2013.
A supporter of deposed Egyptian President Mohamed Morsi shouts slogans during a protest outside Al-Fath Mosque in Ramses Square, Cairo, August 16, 2013.
Supporters of deposed Egyptian President Mohamed Morsi shout slogans and wave Egyptian flags during a protest outside Al-Fath Mosque in Ramses Square, in Cairo, August 16, 2013.
Supporters of Egypt's ousted President Mohamed Morsi carry a coffin, covered with a national flag, of a protester who was killed during Wednesday' clashes in Cairo, August 16, 2013.
Supporters of deposed Egyptian President Mohamed Morsi take part in a protest near Ennour Mosque, Cairo, August 16, 2013.
A soldier holds his weapon as he stands on an armored personnel carrier positioned outside the state-run television station in Cairo, August 16, 2013.
Egyptian army soldiers take their positions at an entrance to Tahrir Square, Cairo, August 16, 2013.
A man who lost relatives in recent violence stands near a list of names of dead members of the Muslim Brotherhood and supporters of deposed Egyptian President Mohamed Morsi at El Eyman mosque in Cairo, August 16, 2013.
A man walks through debris from what is left of burned vehicles outside the Rabaah al-Adawiya mosque, Cairo, August 16, 2013.
Abandoned shoes and a tea glass, belonging to supporters of ousted Egyptian President Mohamed Morsi, remain on a wall outside the Rabaah al-Adawiya mosque, Cairo, August 16, 2013.