At least 100 people were killed Friday after thousands of supporters of deposed President Mohamed Morsi heeded a call by the Muslim Brotherhood to stage a "day of rage" to denounce a government crackdown on demonstrations that killed over 600 people earlier this week.
Morsi supporters and anti-military protesters marched in rallies across the country and were met by government security forces. A curfew came into effect at 5 p.m. GMT, with authorities warning of "firm action" against anyone breaking the curfew.
Eight people were killed in the coastal city of Damietta and four more in Ismailia, east of Cairo, in clashes with the military outside of a court complex, said emergency service official Abdel Wahab Dura.
LIVE UPDATES: Egypt in turmoil
Five people were reported killed in clashes in the city of Fayoum, southwest of Cairo, a local hospital official reported. Another five people died in Alexandria, an official at the local emergency services said. At least 15 people were wounded.
Twenty-four members of the Egyptian police force have died since late last night, a security official said Friday, bringing the number of police killed in political violence to 67 since Wednesday. A police conscript was killed in a drive-by shooting in the north of the capital, state news agency MENA reported.
At least 95 people were killed in Cairo's Ramses square and hundreds were injured after protesters were allegedly fired on by security forces, Al Jazeera's correspondent reported. A witness told Reuters that there were bullet wounds on the bodies that were moved to a Cairo mosque.
Al Jazeera's Simon McGregor Wood said as he was leaving the square he saw a stream of injured people, as well as some dead.
VIDEO: Bullets fly on Cairo streets
When a military helicopter flew low over the area, thousands of Morsi supporters gathered in Ramses Square, held up shoes and chanted, "We will bring Sisi to the ground," and, "Leave, leave, you traitor" -- referring to army chief Gen. Abdel Fatah al-Sisi. Protesters reported that they were being fired on from the helicopters and from windows in surrounding buildings.
The army deployed dozens of armored vehicles on major roads in Cairo, and the Interior Ministry has said police will use live ammunition against anyone threatening state buildings.
Egyptian state television showed footage of men near demonstrators firing weapons from a Cairo bridge, but it wasn't clear whether the men were security forces or Morsi supporters.
More than 600 people have been killed and nearly 4,000 injured since Wednesday, when government forces moved to clear two pro-Morsi encampments in Cairo where the ousted president's supporters had been demonstrating for six weeks demanding his reinstatement.
State TV reported Friday that the Egyptian army had deployed forces to guard "important and vital facilities," and that police would deal firmly with any violations of the law.
On Thursday, Tamarod, the protest group that had organized opposition to Morsi's rule, also encouraged Egyptians to take to the streets Friday "to reject domestic terrorism and foreign interference."
Morsi supporters refuse to accept the July 3 ouster of Morsi following massive rallies castigating his year-long rule. They have demanded the resignation of al-Sisi and the reinstatement of Egypt's first democratically elected president – who is in detention and has not been seen in public since his ouster.
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Egypt's Muslim Brotherhood called for an additional week of daily nationwide protests Friday, raising concerns over when the violence would end.
"We call on the Egyptian people and national forces to protest daily until the coup ends," the group said.
Saudi Arabia's King Abdullah said Friday in a TV message that his country stands with Egypt against "terrorism." He called on Arabs to stand together against attempts to destabilize Egypt.
The Muslim Brotherhood condemned the latest violence, saying that Egypt's interim leaders had "lost their minds" and were devoid of ethics and values. The group said that the coup has failed, and it was time for the leaders to accept that.
The leaders of Germany, France, Britain and Italy urged the European Union on Friday to send a united message condemning the violence in Egypt, with Germany Chancellor Angela Merkel calling on Brussels to review its ties with the country.
Merkel and French President Francois Hollande called for EU foreign ministers to meet next week to discuss the nature of the bloc's ties with Cairo.
"The chancellor explained that in view of the latest developments, the German government would review its relations with Egypt," Merkel's office said after the two leaders spoke by phone.
The United Nations is sending its political affairs chief to Egypt next week to meet with a range of officials including representatives from the Muslim Brotherhood amid the ongoing violence following the army's ousting of Islamist President Mohamed Morsi last month, the world body said on Friday.
U.N. officials said the trip by Jeffrey Feltman, under secretary-general for political affairs and former top U.S. diplomat for the Middle East, will help the world body work out how to respond to the Egypt crisis.
"Mr. Feltman will report to the secretary-general [on the Egyptian crisis], and the secretary-general will take Mr. Feltman's advice into consideration and decide what the next steps are," U.N. spokesman Eduardo del Buey told reporters.
The United States also "strongly condemned" the violence and canceled a joint U.S.-Egyptian military exercise in the wake of the bloodshed.
Al Jazeera and wire services