CAIRO - Egypt's Muslim Brotherhood risks political elimination, with the new army-backed government threatening to ban the Islamist organization after launching a fierce crackdown on its supporters that has killed hundreds. Struggling to stamp its authority on Egypt following the ousting last month of President Mohamed Mursi, the country's new rulers have upped the rhetoric, saying the Arab world's most populous nation is at war with terrorism. More than 700 people have died, most of them backers of Mursi, in four days of violence. That has earned Egypt stiff condemnation from Western nations, uncomfortable with Islamist rule but also with the overthrow of an elected government. The crackdown has, however, drawn messages of support from key Arab allies like Saudi Arabia, which have long feared the spread of Brotherhood ideology to the Gulf monarchies. Blaming a defiant Brotherhood for the bloodshed, Egyptian Prime Minister Hazem el-Beblawi proposed dissolving the group in a move that would force it underground and could usher in mass arrests of its members countrywide. The government said it was studying the possibility. "There will be no reconciliation with those whose hands have been stained with blood and who turned weapons against the state and its institutions," Beblawi told reporters. A statement from the United Nations said Secretary-General Ban Ki-moon condemned attacks on churches, hospitals and other public facilities and called for both sides to resolve the violence. "The secretary-general believes that preventing further loss of life should be the Egyptians' highest priority at this dangerous moment," the statement said. "With such sharp polarization in Egyptian society, both the authorities and the political leaders share the responsibility for ending the current violence."