Tens of thousands of supporters of ousted Egyptian President Mohamed Morsi marched through Cairo Friday demanding his reinstatement, even as the interim government threatened to disperse their protest camps.
State TV reported Friday that Egyptian police are planning to block access to the Rabaa al-Adawiya camp in the north of the capital.
A few thousand Muslim Brotherhood supporters chanted pro-Morsi slogans Friday at the sit-in site.
One Islamist leader, Ahmed Hassan, told the crowd that Morsi supporters are ready to "shed their blood to bring back Mr. Morsi" and protect Egypt's national security.
Witnesses say Brotherhood supporters have erected sandbags and brick barriers to prevent security forces from entering the camp. A group calling itself the Voice of Egyptian Women has warned the Muslim Brotherhood is preparing to use women and children as "human shields" to protect its protest camps and its leaders holed up inside.
The standoff has raised fears of new violence, with Human Rights Watch calling Friday for a halt to any immediate plans to forcibly disperse the protests.
The Egyptian military removed Mr. Morsi -- the country's first democratically-elected president -- last month following days of mass protests against his rule.
The new unrest comes as Washington appeared to offer its strongest endorsement yet of the military ouster. U.S. Secretary of State John Kerry said Thursday the military was "in effect, restoring democracy" when it removed Mr. Morsi -- remarks the Muslim Brotherhood quickly denounced.
Egyptian media reported that US Deputy Secretary of State William Burns was expected in Cairo late Friday. A top European Union diplomat was also in Cairo Friday to meet with the country's new interim leaders.
Egypt's interior ministry urged Muslim Brotherhood supporters Thursday to put an end to the sit-ins themselves, promising them "safe passage" if they were to leave.
But overnight, Mr. Morsi's supporters staged protests in front of the military intelligence building and the Supreme Constitutional Court. The Egyptian Army Friday blocked roads leading to other key government buildings and defense installations.
Sky News Arabiya reported that the Brotherhood's Supreme Guide Mohamed Badie was calling on military officers to "disobey orders." Badie and other top Brotherhood leaders are the subject of arrest warrants for "inciting violence."
Nearly 200 people, mostly supporters of Mr. Morsi, have been killed since the Egyptian military toppled the Islamist leader on July 3. His supporters are demanding his return to the presidency and the restoration of the Islamist-drafted constitution.
Mr. Morsi's Muslim Brotherhood fears the government dispersal of the camps could lead to what it views as another massacre, while officials insist that any police action would remain lawful.
The issue has been complicated by government accusations that some of the demonstrators are armed and intent on causing clashes with security officials.
Earlier this week, Amnesty International acknowledged "violent acts including torture and the use of live weapons" by some Morsi supporters. But the London-based group said this should not be used as a pretext to prevent others from exercising their right to peaceful protest.
The Brotherhood views Mr. Morsi's ouster as a military coup and a return to the era of former President Hosni Mubarak, an ex-military commander who was ousted following a series of protests in 2011.
The country's interim government plans to hold a referendum within five months to ratify amendments to the constitution. Parliamentary elections would take place early next year followed by a new presidential election.