At least 25 people, including three soldiers, were killed in deadly clashes between Christians, Muslims and security forces on Monday in the Egyptian capital, the worst unrest since the uprising that toppled the Mubarak regime.
The violence erupted after Coptic Christians protesting against an attack on a church in Aswan clashed with security forces, forcing authorities to declare curfew in Cairo's iconic Tahrir Square area.
Reports of protesters in the capital being crushed by military vehicles further heightened tensions, BBC said.
Prime Minister Essam Sharaf held an emergency meeting of the cabinet today to contain the crisis as the military rulers ordered a swift probe into the unrest.
"These events have taken us back several steps," Sharaf warned in a televised address.
He said the riots were a setback to the country's already fraught transition to civilian rule.
He put the blame on foreign meddling for the troubles, claiming it was part of a "dirty conspiracy."
The unrest started yesterday outside the state TV building but soon spread to the Tahrir Square, the epicentre of the demonstrations that forced President Hosni Mubarak to step down in February.
Copts comprise almost 10 per cent of the population in Egypt and is considered the largest Christian community in North Africa.