Egypt's president has called for calm between the country's christians and Muslims after at least 17 people were killed in a bomb attack on a church. Officials are blaming foreign-backed terrorists.

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The bombing targeted Christian worshippers gathering to mark the new year at the Coptic Orthodox church in the northern city of Alexandria. At least 17 people were killed and a further 43 injured.

Egyptian officials say there are indications the blast involved "foreign elements". The Interior Ministry said the circumstances of the incident and other recent attacks "clearly indicate that foreign elements undertook planning and execution".

Egypt's President Hosni Mubarak said in an emergency address that "wicked terrorists" were behind the bombing, adding that the terrorists would fail in any plans to destabilise Egypt or divide Muslims and Christians.

I don't know what happened. I was making a call and suddenly I found every body deadly scattered, everybody is bleeding... Amgad Zakaria

The attack has sparked fresh tension between Muslims and Christians in Egypt - with hundreds taking to the streets in protest. Some pelted each other with rocks and cars have been set on fire.

Egyptian riot police attempt to put out fire started by Christians outside a mosque in Alexandria following a church bombing which killed 21. (Reuters)

Police used teargas to disperse angry crowds and dozens of officers surrounded the area to prevent a repeat.

"We sacrifice our souls and blood for the cross," shouted protesting Christians.

One worshipper, Amgad Zakaria, told reporters: "I don't know what happened. I was making a call and suddenly I found every body deadly scattered, everybody is bleeding and I flew away. I was just going out of the church... and this happened."

Christians make up about 10 per cent of Egypt's 79 million people. The country, which is due to hold a presidential election in September, has stepped up security around churches, banning cars from parking directly outside them, after an al-Qaeda linked group in Iraq issued a threat against the Church in Egypt in November.

The Islamic State of Iraq threatened Egypt's church over its treatment of women the group claimed the church was holding after they had converted to Islam.

Kameel Sadeeq, from the Coptic council in Alexandria, said: "People went in to church to pray to God but ended up as scattered limbs. This massacre has al-Qaeda written all over, the same pattern al-Qaeda has adopted in other countries."