Egyptian President Mohamed Morsi has announced a snap referendum on a new constitution that has already deepened divisions in a country still struggling to find its identity more than a year after it emerged from Hosni Mubarak's rule.

Morsi, who has triggered a fresh crisis in Egypt by assuming sweeping powers and pushing the constitution through an Islamist-dominated assembly, called the 15 December vote after tens of thousands of his loyalists rallied in support of the document.