The death toll from the violent clashes – condemned as â€œdeplorableâ€ by US Secretary of State John Kerry – rises to at least 278.
Riot police and army personnel take them up positions during clashes with members of the Muslim Brotherhood and supporters of ousted Egyptian President Mohamed Mursi in Cairo Egypt Injured security official protected by demonstrators
Video has emerged which, although not independently verified, appears to a show an Egyptian security official being saved by protesters from being attacked by other demonstrators.
More than 270 people have been confirmed killed in violence across the country, after Egyptian security forces opened fire as they tried to clear two protest camps loyal to deposed president Mohamed Morsi in Cairo.
A month-long state of emergency has been declared as violence spread from the capital to other parts of the country including the Mediterranean city of Alexandria. The move has been opposed by the US.
A curfew from 7pm to 6am has been declared in Cairo, according to reports, as well as ten other provinces including Alexandria and Suez.
The health ministry put the number of dead at 278 – including 43 police officers – with hundreds more injured.
He added that the police would not allow any more sit-ins across the country.
A media crew is seen next to riot police during clashes with members of the Muslim Brotherhood and supporters of deposed Egyptian President Mohamed Mursi in Giza
Security forces at one of the camps in Cairo
US Secretary of State John Kerry called the events â€œdeplorableâ€.
â€œViolence will not create a roadmap for Egyptâ€™s future. Violence only impedes the transition.â€
He added that the promise of the 2011 revolution has not yet been fully realised.
Egyptâ€™s vice president, Mohamed ElBaradei, has announced his resignation. Hazem Al Beblawi, the Prime Minister, said he remained committed to the democratic process under a civilian state.
Meanwhile two Brotherhood politicians have reportedly been arrested.
Skyâ€™s Middle East Correspondent Sam Kiley, reporting earlier from inside the Rabaa al Adawiya camp in the capital, said it was â€œunder very heavy gunfireâ€ and was a â€œmassive military assault on largely unarmed civilians in very large numbersâ€.
He said government forces were using machine guns, snipers, AK-47 and M16 rifles and were firing into the crowd.
Kiley added: â€œThere are machine gun rounds, and snipers on the roof, that are preventing people from getting any closer to the field hospital (in the camp).
â€œI havenâ€™t seen any evidence yet of any weapons on the side of the pro-Morsi camp. The camp is very full of women and children.â€
He said it was a scene of â€œextreme chaos and bloodshedâ€ and â€œmany hundreds of troops and interior ministry police and special forces are involvedâ€.
Riot police fire tear gas at members of the Muslim Brotherhood and supporters of deposed Egyptian President Mohamed Mursi in Cairo
Riot police fire tear gas at members of the Muslim Brotherhood
â€œThe dead and dying are on the steps of an improvised field hospital. The scenes here are absolutely graphic.
â€œI have covered many wars and this is as severe a battlefield as I have witnessed, with the exception of scenes in Rwanda. There are dozens and dozens of people who have been shot in the head, neck and upper body.â€
Among those reported killed in the camp was Asmaa al Beltagui the 17-year-old daughter of senior Muslim Brotherhood leader Mohamed al Beltagui.
Meanwhile, Egyptian authorities have released video footage taken from a helicopter which it said showed gunmen in the camp firing at security forces.
The unrest spread beyond the capital, as pro-Morsi supporters clashed with police in the Nile Delta cities of Minya and Assiut, as police stations, government buildings and churches were attacked or set ablaze.
In Alexandria, tear gas canisters rained down on a pro-Morsi march in the Sharq neighbourhood, amid repeated bursts of automatic gunfire.
Residents, armed with clubs, came out of their homes and shops to help the police, detaining Morsi supporters and handing them over to officers at the Sharq police station.
Morsi supporters, carrying Egyptian flags and pictures of the deposed leader, then clashed with his opponents on a road carpeted with rocks.
Earlier, riot officers in Cairo backed by armoured vehicles and bulldozers also fired tear gas in the camps at the demonstrators who are demanding Mr Morsi be reinstated as the countryâ€™s leader.
The interior ministry, which is in charge of police, warned its security forces would deal firmly with protesters acting â€œirresponsiblyâ€ and said it would guarantee safe passage to those who want to leave the two sites.
The larger is the Rabaa al Adawiya camp described as a â€˜mini townâ€™ in Nasr City, while the other is in Al Nahda Square outside the main campus of Cairo University in Giza.
The interior ministry later said security forces had â€œtotal controlâ€ over the smaller camp and police have managed to remove most of the tents in the square.
The Muslim Brotherhood that backs ousted Islamist president Mr Morsi claimed over 250 people had been killed and 5,000 hurt in the crackdown, which is almost certain to deepen political turmoil in Egypt.
It urged Egyptians to take to the streets in their thousands to denounce the â€œmassacreâ€.
â€œThis is not an attempt to disperse, but a bloody attempt to crush all voices of opposition to the military coup,â€ Brotherhood spokesman Gehad al Haddad said on Twitter.
The Rabaa al Adawiya protest camp, where several Brotherhood leaders are staying, â€œis calling on Egyptians to take to the streets to stop the massacre,â€ Haddad said.
At least three members of the security forces were confirmed to have died in the crackdown, while the health ministry said nine protesters were killed and over 80 were injured.
The raids came after international efforts failed to mediate an end to a six-week political standoff between Morsiâ€™s supporters and the army-backed government which took power after he was ousted on July 3.
Regional television networks showed images of collapsed tents and burning tyres at both sites, as well as protesters being arrested and led away by troops.
A television feed by a pro-Morsi TV station showed thousands of protesters gathered at the centre of the Nasr City site, with many covering their faces to fend off the tear gas.
It said most of the protesters at the other camp fled to the nearby Orman botanical gardens and inside the sprawling university campus.
British Foreign Secretary William Hague said he was â€œdeeply concerned at the escalating violence in Egypt, and regret the loss of life on all sidesâ€.
He added: â€œI condemn the use of force in clearing protests and call on the security forces to act with restraint.â€
Qatar, Turkey and Iran were among the other countries criticising the deadly crackdown.