Angry Coptic Christians in Egypt have clashed with riot police, a day after 21 Christians were killed in a bomb attack during a New Year's Eve service at a Coptic church in Alexandria.
Hundreds of Christian protesters in Alexandria and Cairo have demanded that the authorities do more to protect their community from attacks.
The authorities are questioning seven people over the blast, which they've blamed on foreign elements.
The top Muslim cleric in Egypt, Sheikh Ahmed al Tayeb, has accused Pope Benedict of interfering in Egypt's internal affairs.
The Vatican has rejected the accusation.
In a televised address, President Hosni Mubarak said the bombing bore the hallmark of "foreign hands" seeking to destabilise Egypt. "This act of terrorism shook the country's conscience, shocked our feelings and hurt the hearts of Muslim and Coptic Egyptians," he said.
Muslim leaders also called for unity. The Muslim Brotherhood said no religion in the world could condone such a crime.
Christians in the Coptic Orthodox Church make up about 10% of Egypt's population.