At least 525 people were killed in nationwide violence sparked by a crackdown on the protest camps of supporters of ousted Islamist president Mohamed Morsi, a health ministry official told AFP.
Hundreds of supporters of Egypt's Muslim Brotherhood stormed a government building in Cairo and set a fire at its entrance despite a crackdown on the movement by security forces, state TV and witnesses said, Reuters has reported.
The Brotherhood called for a march in Cairo on Thursday, a day after bloody crackdown on its supporters who occupied protest camps demanding the reinstatement of president Mohamed Morsi.
The Brotherhood said the planned march would set off from the Al-Iman mosque in the capital "to protest the death of their relatives".
Morsi's Muslim Brotherhood spoke of 2,200 dead overall and more than 10,000 wounded.
Rafah border "indefinitely" closed
Egyptian authorities have closed the Rafah border crossing with the Gaza Strip "indefinitely" for security reasons after a day of deadly violence nationwide," a security official told AFP on Thursday.
Hundreds of Palestinian travellers were left stranded on both sides of the crossing, the only gateway into the Hamas-ruled Palestinian territory that bypasses Israel, witnesses said.
State of emergency
The army-backed interim government imposed a month-long nationwide state of emergency, and curfews in Cairo and 13 other provinces after the violence on Wednesday. Gory photographs and video images of the Cairo bloodbath dominated social media networks, as world powers called for restraint and condemned the show of force by security forces.
At least four churches were attacked, with Christian activists accusing Morsi loyalists of waging "a war of retaliation against Copts in Egypt".
Hours after tear gas canisters first rained down on tents of protesters in the sprawling Rabaa al-Adawiya camp in eastern Cairo, an AFP correspondent counted at least 124 bodies in makeshift morgues there.
In a field hospital, its floors slippery with blood, doctors struggled to cope with the casualties, leaving the hopeless cases, even if still alive.
Among those killed in Cairo was 17-year-old Asmaa al-Beltagui, daughter of wanted Muslim Brotherhood leader Mohammed al-Beltagui, a spokesman for Morsi's movement said.
Britain's Sky News said a veteran cameraman, Briton Mick Deane, was shot and killed while covering the assaults.
El Baradei resigns
The violence prompted vice president and Nobel laureate Mohamed ElBaradei to resign, saying his conscience was troubled over the loss of life, "particularly as I believe it could have been avoided".
"It has become too difficult to continue bearing responsibility for decisions I do not agree with and whose consequences I fear," he said.
Shortly after dawn on Wednesday, witnesses and an AFP correspondent said security forces fired tear gas before surging into Rabaa al-Adawiya, sparking pandemonium among the thousands of protesters who had set up the camp soon after Morsi was ousted in a military coup 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).
Many Morsi supporters were given safe passage out of the camp, some flashing victory signs as they left through a security corridor.
A security official told AFP that hundreds of people were taking advantage of the safe passage offer, but that some diehards had stayed behind to fight on.
By Wednesday evening, a security official said Rabaa al-Adawiya was "totally under control", adding: "There are no more clashes".
In the smaller of the protest camps, at Al-Nahda square in central Cairo, police said they had control of the area after two hours.
Television footage showed flattened tents, as women and children flanked by police and army troops were led out of the square.
Authorities later said calm had been restored across the country.
Use of force widely condemned
Europe's leading powers, along with Iran, Qatar and Turkey, strongly denounced the use of force by the interim government.
The White House said Washington, which provides Egypt with $1.3 billion in annual military aid, "strongly condemns" the violence against the protesters and opposes the imposition of a state of emergency.
Interim prime minister Hazem al-Beblawi praised the police for their "self-restraint" and said the government remained committed to an army-drafted roadmap that calls for elections in 2014.
The 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.
Interior Minister Mohamed Ibrahim said no more protests would be tolerated.