Hundreds of rioters attacked the campaign headquarters of an Egyptian presidential candidate who's up against the Muslim Brotherhood's candidate.

Former Egyptian Premier Ahmed Shafiq will face off with the Muslim Brotherhood's Mohammed Morsi in an election runoff June 16-17.

The pair were announced as the top vote-getters in last week's first round of voting. Shafiq is widely viewed by opponents as an extension of the regime of ousted President Hosni Mubarak, and the Morsi-Shafiq runoff is the most polarizing contest possible.

Soon after the announcement, the protestors attacked Shafiq's campaign office, smashing windows, trashing campaign signs and posters, and setting the building on fire.

Shafiq's supporters blame the powerful Muslim Brotherhood for the violence. "It's a crime. They are criminals. This is not freedom," counterprotestor Almel Ibrahim said.

After the attack, Shafiq supporters came to the site and shouted, "The Muslim Brotherhood are God's enemies. Down down Morsi."