A group supporting deposed Egyptian President Mohamed Morsy called for a million-man march from 33 mosques Friday amid concerns that tensions could erupt into further violence.
The Anti-Coup Prodemocracy Alliance is behind the planned march under the banner of "Egypt against the coup," which was announced in a statement Thursday. It is expected to start after noon prayers.
The group also urged "all free people in all countries of the world to demonstrate peacefully" in support of their marches.
Its call to action comes after Egypt's Interior Ministry on Thursday urged pro-Morsy protesters to leave two Cairo squares and guaranteed they would have a safe exit.
The protests represent a threat to national security and traffic congestion, Information Minister Durriya Sharaf el-Din said Wednesday.
Interim Interior Minister Mohamed Ibrahim was authorized to take "all necessary measures to face these dangers and end them," el-Din said.
The minister's statement has been widely interpreted by local media outlets as a green light for security forces to disperse the thousands of protesters taking part in sit-ins at squares in Rabaa al-Adawiya and Nahda Masr.
A visiting African Union delegation went to the Rabaa al-Adawiya sit-in Thursday night.
Earlier, the group Human Rights Watch urged the government to order a halt to any immediate plans to break up the Muslim Brotherhood sit-ins 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," said Nadim Houry, deputy Middle East director at Human Rights Watch.
Houry warned that the number of protesters packed together in the squares means "hundreds of lives could be lost if the sit-in is forcibly dispersed."
The warning from Human Rights Watch echoed one issued by fellow rights group Amnesty International on Wednesday.
"Given the Egyptian security forces' record of policing demonstrations with the routine use of excessive and unwarranted lethal force, this latest announcement gives a seal of approval to further abuse," said Hassiba Hadj Sahraoui, deputy director for the Middle East and North Africa at Amnesty International.
U.S. State Department deputy spokeswoman Marie Harf said Thursday that the United States is concerned by reports that government critics in Egypt are being denied the right to peaceful protest.
"It's essential that the security forces in the interim government respect the right of peaceful protest, including the ongoing sit-in demonstrations," she said.
But remarks by U.S. Secretary of State John Kerry in an interview with CNN's Pakistan affiliate GEO TV Thursday have angered some Morsy supporters.
Asked why the United States is "not taking a clear position" on the Egyptian military's intervention to depose the democratically elected Morsy, Kerry replied, "The military was asked to intervene by millions and millions of people, all of whom were afraid of a descendance into chaos, into violence.
"And the military did not take over, to the best of our judgment so -- so far. To run the country, there's a civilian government. In effect, they were restoring democracy."
Muslim Brotherhood spokesman Gehad El-Haddad denounced Kerry's words and accused the Obama administration of being "complicit in the military coup."
"Is it the job of the army to restore democracy?" he asked.
He then queried whether Kerry would accept the removal of the U.S. government by the military if large protests took place there.
"Such rhetoric is very alarming. The American people should stand against an administration that is corrupting their values in supporting tyranny and dictatorship," he said.
Visits to Morsy
Since Morsy was ousted from office on July 3, hundreds of people have been killed and thousands more wounded as tensions have flared into violence.
The former Muslim Brotherhood leader became Egypt's first democratically president in June 2012 but soon found himself at odds with the opposition. After mass protests, the military removed him from power and detained him last month, and he has not been seen publicly since.
However, the high-level African Union delegation and EU foreign policy chief Catherine Ashton have met with Morsy and the leaders who replaced his Muslim Brotherhood administration as part of international efforts to ease the bubbling tensions within Egypt.
On its official website, the Muslim Brotherhood cited the African Union delegation as saying it had spent two hours with Morsy and that the visit had been good. The delegation plans to visit him again, the Brotherhood said.
An aide to Ashton also visited the Rabaa al-Adawiya sit-in on Wednesday, Haddad said via Twitter.
Morsy is being held in relation for a jailbreak that took place during Egypt's 2011 revolution but well before he came to power, state media reported.
Away from the capital, a hotel in Egypt's North Sinai region was hit by an explosion late Thursday, state media reported.
The blast went off at the Sinai Sun hotel in the town of Al-Arish about midnight, sending smoke billowing into the air, Egypt's official Ahram Online reported.
No one was injured in the blast, according to state-run news agency EGYNews. But earlier Thursday, a policeman was shot dead in an attack at the same hotel, Ahram Online said. It's not clear who was responsible for either incident.
CNN's Schams Elwazer contributed to this report.