Defying an order from Egypt’s interim government that supporters of ousted president Mohamed Morsi end sit-ins in Cairo, the Anti-Coup Alliance called for a million-man march from 33 mosques Friday.
The group’s rejection of the government’s offer of safe passage if they left the two squares voluntarily raised concerns that the Morsi supporters were headed for a bloody showdown with Egyptian security forces.
Egyptian officials said they would break up the Muslim Brotherhood demonstrations "soon," but declined to provide details.
By Friday afternoon, limited clashes had been reported after tens of thousands of Morsi supporters filled the streets of Cairo.
Later, police moved in and blockaded the sit-ins, allowing people out, but not into the camps.
Protesters have gathered at three locations in Cairo, BBC said.
News that three top Muslim Brotherhood leaders, including Supreme Guide Mohamed Badie, would be referred to trial for incitement to murder, has also raised tensions.
Human Rights Watch has urged the government to abandon plans to remove protesters by force and "deal peacefully with any problems arising."
"To avoid another bloodbath, Egypt's civilian rulers need to ensure the ongoing right of protesters to assemble peacefully, and seek alternatives to a forcible dispersal of the crowds," Nadim Houry, deputy Middle East director at Human Rights Watch, said, according to CNN. “Hundreds of lives could be lost if the sit-in is forcibly dispersed."
Meanwhile, US Secretary of State John Kerry has been criticized for remarks he made in an interview with CNN's Pakistan affiliate GEO TV Thursday. "The military did not take over, to the best of our judgment so — so far,” he said. “To run the country, there's a civilian government. In effect, they were restoring democracy."
Muslim Brotherhood spokesman Gehad El-Haddad challenged Kerry's interpretation of Morsi’s removal from office and accused the Obama administration of being "complicit in the military coup."
More from GlobalPost: Egypt: Morsi supporters reject offer for 'safe exit' if they end sit-in protests
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