Gunfire has erupted around a Cairo mosque where hundreds of protesters have barricaded themselves inside.
Video from the scene has shown security forces shooting towards Al-Fatah Mosque near Ramses Square and chaos inside of the building as people seek cover.
Security forces and protesters inside of the mosque have been in a tense standoff. The protesters have been stranded in the mosque for hours following a day of demonstrations.
Earlier, police offered to evacuate the women from the Al-Fatah Mosque but insisted on questioning the men. The protesters rejected that offer, leading to a tense standoff.
Meanwhile, an Egyptian government spokesman says 173 people have been killed since Friday's nationwide protests by supporters of ousted President Mohamed Morsi.
In a Saturday news conference carried on Egyptian state television, the spokesman said 57 security force officers were among those killed.
He expressed his "regret" for the deaths, which he blamed on clashes between "terrorist" operations and civilians, not the direct involvement of police and security forces.
Friday's unrest began after Morsi supporters emerged from midday prayers to hold a "Day of Rage."
The protests led to clashes between Morsi supporters and security forces. Civilians armed with weapons also fought protesters. The clashes spread across the country.
Video showed residents pelting Morsi's Muslim Brotherhood supporters with rocks, as well as plain-clothed Egyptians firing at each other in running street battles. The Muslim Brotherhood said a military aircraft opened fire on demonstrators.
More than 700 people have been killed since Wednesday's government crackdown on two pro-Morsi camps in Cairo.
The government said 638 people were killed during the crackdown, but the Muslim Brotherhood said the death toll was in the thousands.