Cairo: Deeply polarised Egypt braced for renewed confrontation on Friday after the Muslim Brotherhood called for a nationwide march of millions to show anger at a ferocious security crackdown on Islamists in which hundreds were killed, Reuters reported on Friday.
Defying criticism from major Western allies, Egypt's army-backed government warned it would turn its guns on anyone who attacked the police or public institutions after protesters torched a government building in Cairo on Thursday.
At least 623 people died and thousands were wounded on Wednesday when police cleared out two protest camps in Cairo set up to denounce the military overthrow on July 3 of Egypt's first freely elected president, Islamist leader Mohamed Mursi.
It was the third mass killing of Mursi supporters since his ouster. The assault left his Muslim Brotherhood in disarray, but they warned they would not retreat in their showdown with army commander General Abdel Fattah al-Sisi.
"After the blows and arrests and killings that we are facing, emotions are too high to be guided by anyone," said Brotherhood spokesman Gehad El-Haddad.
A statement from the Brotherhood called for a nationwide "march of anger" by millions of supporters on Friday after noon prayers.
"Despite the pain and sorrow over the loss of our martyrs, the latest coup makers' crime has increased our determination to end them," it said.
The Brotherhood accuses the military of staging a coup when it ousted Mursi. Liberal and youth activists who backed the military saw the move as a positive response to public demands.
Friday prayers have proved a fertile time for protests during more than two years of unrest across the Arab world.
In calling for a "Friday of anger," the Brotherhood used the same name as that given to the most violent day of the 2011 uprising against former President Hosni Mubarak. That day, January 28, 2011, marked the protesters' victory over the police, who were forced to retreat while the army was asked to step in.
In a counter move, a loose liberal and leftist coalition, the National Salvation Front, called on Egyptians to protest on Friday against what it said was "obvious terrorism actions" conducted by the Muslim Brotherhood.
Signalling his displeasure at the worst bloodshed in Egypt for generations, U.S. President Barack Obama said on Thursday normal cooperation with Cairo could not continue and announced the cancellation of military exercises with Egypt next month.
"We deplore violence against civilians. We support universal rights essential to human dignity, including the right to peaceful protest," he said, taking a brief break from his holidays to deliver the sharp rebuke.
The United States on Thursday renewed a warning to its citizens to leave Egypt because of the ongoing unrest. It issued the same advice last month.
The Egyptian presidency issued a statement saying Obama's remarks were not based on "facts" and would strengthen and encourage violent groups that were committing "terrorist acts."