CAIRO (CNN) — The Muslim Brotherhood said Thursday that nothing will stop its "glorious revolution" in Egypt -- not even the deaths of more than 500 people killed in the country's bloodiest day in recent history.
"We will continue our sit-ins and demonstrations all over the country until democracy and the legitimate rule are restored in Egypt," said Essam Elerian, a senior member of the Islamist movement.
Egypt's short-lived experiment with democracy took a gruesome turn Wednesday, culminating in mass carnage and a return to the repressive state of emergency that had gripped the country for 30 years.
Exactly what sparked the bloodshed depends on who you ask.
Protesters in Cairo who support ousted President Mohamed Morsy said security forces waged a "full-on assault" on what they said had been peaceful demonstrations calling for Morsy's restatement. Many of the protesters also support the Muslim Brotherhood.
Egypt's interim government, however, said it was trying to disperse protesters peacefully -- but had to retaliate when some protesters turned violent.
CNN journalists on the ground said many of the protesters injured or killed were unarmed.
By the end of the day, at least 525 people were killed and more than 3,700 injured in clashes in the country Wednesday, the health ministry said.
Those killed include 43 police officers, the interior ministry said.
It was the bloodiest day since the 2011 revolution to oust Morsy's predecessor, Hosni Mubarak.
A tense calm
The violence spilled over into Thursday, with state-run TV reporting Morsy supporters attacking police stations, hospitals and government buildings in areas outside Cairo.
But Cairo streets were relatively calm Thursday morning -- partly due to Egypt's new state of emergency.
The military-backed interim government declared a month-long state of emergency Wednesday, which bars people from gathering without prior permission and lets police jail them indefinitely.
It's the kind of stifling police state that the nation lived through under Mubarak -- before he was thrown out of office in a popular uprising in 2011.
The tumult left other countries uneasy.
France and Germany have summoned the Egyptian ambassadors to their countries to discuss the turmoil. And Pope Francis deplored the violence.
"We pray together for peace, dialogue and reconciliation in that beloved land and in the whole world," the pope said Thursday.
And the United States is considering canceling next month's planned biennial military training exercise with Egyptian forces, a presidential administration official said.
Security forces raided the pro-Morsy camps Wednesday after weeks of simmering tension. Clashes and gunfire broke out, leaving pools of blood and bodies strewn all over the streets.
Authorities bulldozed tents and escorted hundreds of people away. Some mothers and fathers managed to whisk away their children, gas masks on their faces.
The dead included cameraman Mick Deane, who'd worked for UK-based news channel Sky News for 15 years and for CNN before that.
But the fighting wasn't limited to the capital.
Morsy supporters reportedly besieged churches in Sohag, setting fire to Saint George's Church, a tour bus and a police car, state media reported.
At least 84 people, including Muslim Brotherhood members, have been referred to military prosecutors for charges including murder and the burning of churches, the state-run EGYNews site reported.
But protesters vowed to remain defiant until Morsy is reinstated.
Elerian, the senior Muslim Brotherhood member, said he's not deterred by calls for his arrest.
"They can arrest me and 100 of us, but they can't arrest every honorable citizen in Egypt," Elerian told CNN Thursday. "They can't stop this glorious revolution."
Morsy's rise, fall
Morsy, a former leader in the Muslim Brotherhood, became Egypt's first democratically elected president in 2012. He replaced Mubarak, who kept a firm grip on power for 30 years.
But rather than uniting Egypt after Mubarak's fall, divisions intensified during his time as president.
Critics accused him of being authoritarian, trying to force the Muslim Brotherhood's Islamic agenda on the country and failing to deliver freedom and justice.
Morsy's supporters say the deposed president wasn't given a fair chance, and say his backers have been unfairly targeted for expressing their opinion.
Though Morsy has not appeared in public since he was taken into custody, his supporters have amassed on the streets nationwide to slam military leaders and demand his reinstatement.
Even Egypt's interim government suffered a major setback after the raid.
Mohammed ElBaradei -- a secular leader who was one of Morsy's biggest critics -- submitted his resignation Wednesday as vice president.
ElBaradei said he didn't agree with the decisions carried out by the ruling government and "cannot be responsible for a single (drop of) blood."
CNN's Reza Sayah reported from Cairo; Holly Yan wrote from Atlanta. CNN's Ian Lee and Frederik Pleitgen also contributed to this report.
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