An Egyptian Coptic Christian, centre-right, observes the scene, wrapped in a sheet on which a Christian cross has been painted in blood outside Saints Church in Alexandria. (Ben Curtis/Associated Press)

Egyptian President Hosni Mubarak has called for national unity after the deadly New Year's Eve bombing of a Christian church in Alexandria.

Mubarak appeared on national television Saturday to condemn the attack, which killed at least 21 people and wounded 79 others. He blamed the explosion on "foreign hands" seeking to undermine Egypt's security, stability and unity.

He called on both Christians and Muslims to "close ranks and confront the forces of terrorism," the state news agency MENA said.

A woman grieves outside the Coptic Christian Saints Church in the Mediterranean port city of Alexandria on Saturday. (Tarek Fawzy/Associated Press)

Officials say a suicide bomber attacked early Saturday as worshippers were emerging from the Coptic Christian Saints Church.

Afterward, Christians clashed with police and stormed a nearby mosque. The protest sparked clashes with Muslims, and both sides began throwing stones and bottles at each other in the street.

More clashes erupted later in the day as young men hurled stones in the streets outside the church. Witnesses say several protesters were struck by rubber bullets fired by riot police.

The blast came from a car parked outside the church, but police were still looking into whether the car had been rigged with explosives or a bomb had been placed under it.

Witnesses reported seeing the charred chassis of the car, with the remains of several bodies nearby and dozens wounded.

The explosion occured outside a church in the
northern port city of Alexandria, Egypt.

Health Ministry official Osama Abdel-Moneim said most of the people killed were Christians. The blast mangled at least six cars on the street, setting some ablaze.

The attack comes at a time of rising sectarian tension in Egypt and the broader region.

In November, hundreds of Christians rioted in Cairo, smashing cars and windows after police violently stopped the construction of a church.

The rare outbreak of Christian unrest in the capital left one person dead.

Christians are believed to make up about 10 per cent of Egypt's mainly Muslim population of nearly 80 million, and are increasingly protesting acts of discrimination.

The Alexandria governor accused al-Qaeda for the bombing, pointing to the terror network's branch in Iraq, which has carried out a string of attacks on Christians there and has threatened Egypt's Coptic Orthodox Christian community as well.

Egypt's government has long insisted that the terror network does not have a significant presence in the country, and it has never been conclusively linked to any attacks in the north African country.

With files from The Associated Press