Sarah Lynch, Special for USA TODAY
CAIRO - Egypt braced for more turmoil Friday as protesters planned to take to the streets two days after more than 600 people were killed in violence that spewed across the country.
Supporters of ousted President Mohammed Morsi vowed to gather in locations across the uneasy capital to denounce what they see as a wave of cruel injustices since July 3, when Gen. Abdel Fattah Al-Sisi overthrew the leader.
Marches will move from "all mosques of Cairo" and head toward Ramses Square after midday prayer in a "Friday of Anger," Muslim Brotherhood spokesman Gehad El-Haddad said on Twitter.
"We are going to protest and continue protesting until we reach our goals," said Ashraf Abdel Ghaffar, of the Brotherhood.
Marwa Othman, 25, a masters student, vowed that protesters Friday "will not be silenced."
"We want our democracy back," she said outside the Al-Iman mosque in Nasr City Thursday afternoon where hundreds of bodies were held before being moved and buried.
The dead came from a nearby protest camp that was crushed by security forces starting early Wednesday morning. Bodies were wrapped in bloody white sheets and chilled with melting bags of ice. One by one, they were carried out of the mosque in wooden coffins.
"We feel we are under arrest," said Osama Mahmoud, 44, in a crowd that gathered outside the mosque and erupted into chants against the military and police. Some held posters of Morsi.
Ahmed Abou Anan, 31, who handed out sandwiches to mourners and people who came to show their support, said he would ask God to kill the army chief, Sisi.
"It's still a dream of Egyptians to feel freedom," said Motaz Ismail, 41, a manager at a chemical trading company. "We will not stop at this death."
At least 638 were killed nationwide Wednesday including 43 police, the health ministry told the Associated Press. Most died in violence at two main protest sites positioned on opposite sides of the capital. With bulldozers, tear gas and live ammunition, security forces tore through the sit-ins, where protesters gathered for six weeks denouncing the military coup and demanding Morsi's reinstatement.
Nine rights groups condemned the use of excessive force.
"The security apparatus could have avoided this human tragedy if it had complied with international rules and standards for the dispersal of assemblies," said a joint statement by the groups.
But the government defended its position, saying it gave protesters a chance to leave and was "keen to adopt a gradual plan to avoid bloodshed and falling of victims."
"All ways to peacefully end the two sit-ins were in vain," a State Information Service statement said, adding that suggested initiatives to do so were welcomed but rejected by leaders of the Muslim Brotherhood.
As the dust cleared Thursday, anger raged. Demonstrators attacked and torched a government building in Giza not far from the second protest site, which by Thursday was completely cleared and the roads open to traffic. A fire engine that came to quell the flames was set alight.
Attacks on churches continued for a second day, Coptic Christians reported, as Islamists direct their anger at Christians for the protest dispersals. Islamists also accused them of conspiring to overthrow Morsi.
On Wednesday, 21 police stations were stormed, the interior minister had said, and in recent weeks, militants in the restive Sinai Peninsula escalated deadly assaults on security forces.
Some expect more retaliatory attacks.
"Once the cycle of violence starts it's hard to stop it," said Shadi Hamid, director of research for the Brookings Doha Center.
"When you close off all opportunities for political participation and expression people are likely to resort to violence and we're seeing that play out right now," he said.
The State Department on Thursday urged U.S. citizens living in Egypt to depart and warned Americans to defer travel to the country "because of the continuing political and social unrest." Last month the State Department ordered non-emergency government personnel and their families to leave Egypt.
It urged those who will stay to comply with location regulations, which include a 7 pm to 6 am curfew under a recently-declared state of emergency.
On Thursday, the U.S. canceled a joint military exercise with Egypt and President Obama condemned the violence.
"While we want to sustain our relationship with Egypt, our traditional cooperation cannot continue as usual when civilians are being killed in the streets and rights are being rolled back," Obama said Thursday, speaking from his weeklong vacation in Martha's Vineyard, according to the AP.
But the Working Group on Egypt - comprised of eleven policy advisors, co-chairs, executives, directors and senior fellows at Freedom House, the Council on Foreign Relations and nine other institutes - called on the Obama administration to take further steps, including immediate suspension of military aid that totals $1.3 billion annually.
Washington has refused to call the military takeover in Egypt a coup, which would require the U.S. to halt funding.
"The killing of hundreds of protesters carried out by the Egyptian military government was unnecessary, unjustified, and in contravention of international human rights standards," the Working Group on Egypt said in a statement. "These events demand a shift in U.S. policy that is urgent and long overdue."