Egyptian security forces surrounded a Cairo mosque early Saturday where about 1,000 protesters are trapped inside.
The Brotherhood, which backs deposed President Mohammed Morsi, has called for a week of daily rallies.
The protesters are stranded in the mosque following a day of violent demonstrations that Egypt\’s Muslim Brotherhood says it will hold until ousted president Mohamed Morsi is reinstated. Some 100 people across the country were killed in the bloody demonstrations Friday.
TV stations are reporting that security forces had entered to negotiate with the Islamist protesters to persuade them to leave. The protesters have rejected that offer.
Live television pictures showed security forces in riot gear on the steps outside, but with no sign of violence.
Both sides have been accusing the other of opening fire, with security forces saying "armed elements\’ in the mosque were shooting them. The protesters say it is security personnel carrying out the attacks.
Meanwhile, Egypt\’s interim officials say more than 1,000 Islamists were arrested on Friday, the AFP news agency reports.
On Friday, chaos descended on Egypt, including its capital, Cairo, where 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.
Health officials said most of the victims died in and around Cairo\’s Ramses Square. Witnesses said they saw many bodies laid out in mosques that have become makeshift morgues. Several policemen were among the dead.
Clashes were also reported in Alexandria, Fayoum, Suez, Ismailia, Tanta and El Arish.
Video showed residents pelting 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.
With Friday\’s death toll, 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.
Earlier Friday, Egyptian state media warned people to stay off the streets in Cairo as an operation to confront what it called "terrorist elements" unfolds.
Also Friday, two prominent U.S. senators, John McCain and Lindsey Graham, urged U.S. President Barack Obama to suspend all aid to Egypt. The U.S. gives Egypt about $1.3 billion in military aid each year.
Obama has canceled next month\’s military exercises with Egypt. He said traditional cooperation cannot continue when civilians are dying in the streets.
Meanwhile, the U.N. announced it was sending its political affairs chief Jeffrey Feltman to Egypt next week for consultations with Egyptian authorities.
French President Francois Hollande and German Chancellor Angela Merkel have called for European Union foreign ministers to meet next week to discuss Egypt\’s crisis. In a Friday statement, they also called for an immediate end to the unrest.
U.S. President Barack Obama has canceled next month\’s scheduled military exercises with Egypt. He says traditional cooperation cannot continue when civilians are being killed in the streets.
But some other nations support the interim government\’s actions.
Saudi Arabia\’s King Abdullah issued a statement saying: "The Kingdom of Saudi Arabia, its people and government stood and stands by today with its brothers in Egypt against terrorism."
Security was tight in Cairo, with many armoured personnel carriers on the streets.
The army blocked off entrances to Tahrir Square, the focus of demonstrations that led to the toppling of President Hosni Mubarak in 2011.
Morsi, Egypt\’s first democratically elected president, was ousted by the military on 3 July.
He is now in custody, accused of murder over a 2011 jailbreak. His period of detention was extended by 30 days on Thursday.