CAIRO – An angry Mohammed Morsi refused Thursday to call off a referendum on a disputed constitution that has sparked Egypt's worst political crisis in two years, drawing chants of "topple the regime!" from protesters who waved their shoes in contempt.

The Egyptian president's uncompromising stand came a night after thousands of his supporters and opponents fought pitched battles outside his Cairo palace, leaving at least six dead and 700 injured.

Speaking in a nationally televised address, Morsi accused some in the opposition of serving remnants of Hosni Mubarak's authoritarian regime and vowed he would never tolerate anyone working for the overthrow of his "legitimate" government.