Dozens of people were wounded by the blast, which scattered body parts, destroyed cars and smashed windows. The attack prompted Christians to protest on the streets, and some Christians and Muslims hurled stones at each other.

Egypt has stepped up security around churches, banning cars from parking outside them, since an al Qaeda-linked group in Iraq issued a threat against the Church in Egypt in November.

Egypt's leaders were quick to call for unity, wary of any upsurge in sectarian strife or other tension as the country approaches a presidential election due in September amid some uncertainty about whether President Hosni Mubarak, 82, will run.

Mubarak promised in a televised address that terrorists would not destabilize Egypt or divide Christians and Muslims. He said the attack "carries evidence of the involvement of foreign fingers" and vowed to pursue the perpetrators.

A statement on an Islamist website posted about two weeks before the blast called for attacks on Egypt's churches, listing among them the one hit. No group was named in the statement.