Cairo: Security forces moved in Wednesday on two huge Cairo protest camps set up by supporters of Egypt's ousted president Mohammed Morsi, launching a crackdown that quickly turned into a bloodbath with dozens dead.
Less than three hours after the first tear gas canisters rained down on tents of protesters in the sprawling Rabaa al-Adawiya camp in east Cairo, an AFP correspondent counted at least 43 bodies in a makeshift morgue set up by medics manning a field hospital and treating scores of wounded. All of the dead were males, many killed by gunfire.
The operation began shortly after dawn when security forces surrounded Rabaa al-Adawiya and a similar protest at Al-Nahda square, in the centre of the capital. 
Witnesses said after firing tear gas security forces surged into Rabaa al-Adawiya, sparking pandemonium among the thousands of protesters who had set up the camp soon after Morsi was ousted by the army on July 3.
Men in gas masks rushed to grab each canister and dunk them in containers of water, as the main stage near the mosque of the camp blared Islamic anthems and protesters chanted "Allahu Akbar" (God is greatest.)
Clashes quickly erupted between protesters and security forces on one side of the camp, with automatic fire reverberating across the square. It was not immediately clear who was doing the shooting.
Television footage showed the injured being carried to a makeshift medical centre as well as police dragging away protesters, who have defied numerous ultimatums by the army-installed authorities to end their demonstrations.
Protest leaders wearing gas masks stood defiantly on a stage while crowds of people wearing face masks stood amid the swirling tear gas as bulldozers began dismantling the camp.
Police barred journalists not already in the camp from entering. Egypt's interior ministry said some two hours into the operation that security forces have "total control" over Al-Nahda Square, the smaller of the two camps.
"Police forces have managed to remove most of the tents in the square," the ministry said.
A security official told AFP that dozens of Morsi supporters had been arrested with the help of residents of the area.
Television footage showed protesters who had been rounded up sitting in the ground handcuffed and surrounded by security forces. Families, with their children, carrying plastic bags were seen being escorted out of the square by police.
Soon after the police launched the crackdown, angry Morsi supporters blockaded some streets of the capital and set tyres ablaze, sending black smoke billowing across the sky.
Morsi's Muslim Brotherhood urged Egyptians to take to the streets in their thousands to denounce the "massacre".
"This is not an attempt to disperse, but a bloody attempt to crush all voices of opposition to the military coup," Brotherhood spokesman Gehad al-Haddad said on Twitter.
The Rabaa al-Adawiya protest camp, where several Brotherhood leaders are staying, "is calling on Egyptians to take to the streets to stop the massacre," Haddad said.
In a separate tweet, Haddad said at least 250 people were killed and over 5,000 injured in the crackdown. There was no immediate independent confirmation of the tolls.
Egypt's interior ministry said two members of the security forces were killed in the operation. Railway authorities announced that all trains had been grounded to prevent protesters from moving outside of Cairo and reassembling.
In a reprisal attack, Morsi's supporters torched a church in central Egypt, MENA state news agency said. The assailants threw firebombs at Mar Gergiss church in Sohag, a city with a large community of Coptic Christians who comprise up to 10 percent of Egypt's 84 million people, causing it to burn down, the agency said.
Wednesday's crackdown came just hours after the United States urged the military-backed interim government to allow Morsi supporters to protest freely.
State Department deputy spokeswoman Marie Harf said Washington regarded freedom to protest as a "key part" of the democratic process but would be concerned by reports of violence.
The United States, which provides $1.5 billion in mostly military aid to Egypt every year, maintains close ties to the Egyptian military but says it favours a rapid return to elected civilian rule.
Morsi, Egypt's first elected president, was overthrown by the military on July 3 with popular backing. His supporters had said nothing short of his reinstatement would persuade them to disperse.
Clashes between pro- and anti-Morsi demonstrators and security forces have killed more than 250 people since the end of June.
On Monday, the judiciary extended Morsi's detention for a further 15 days pending an investigation into his collaboration with Palestinian group Hamas.
The Muslim Brotherhood, banned in 1954 and repressed by successive governments, won both parliamentary and presidential elections in 2011 after the ouster of veteran strongman Hosni Mubarak.
Prosecutors have set an August 25 date for the trial of the Brotherhood Supreme Guide Mohammed Badie and his two deputies.