The Muslim Brotherhood defiantly called for a week of protests across Egypt starting on Saturday, a day after more than 100 people died in clashes between Islamists and the security forces that pushed the country ever closer to anarchy, Reuters said.

Undeterred by the bloodshed in which about 700 have been killed since Wednesday, August 14 the Brotherhood urged its supporters back onto the streets to denounce the overthrow of Islamist President Mohamed Morsi and a crackdown on his followers.

Many Western allies have denounced the killings, including the United States, but Saudi Arabia threw its weight behind the army-backed government on Friday, accusing its old foe the Muslim Brotherhood of trying to destabilize Egypt.

Violence erupted across Egypt after the Brotherhood, which has deep roots in the provinces, called for a "Day of Rage". Roughly 50 people died in Cairo and more than 20 in the country's second city, Alexandria, security sources said.

The Brotherhood announced a series of daily rallies over the next six days, starting on Saturday.

An interim cabinet, installed by the army after it removed Morsi during rallies against his often chaotic rule, has refused to back down. It has authorized police to use live ammunition to defend themselves and state installations.