The death toll in a car bomb explosion in front of a church in Egypt's northern city of Alexandria has risen to 21, a church source told Xinhua.

A car bomb exploded in front of a church in Egypt's northern city of Alexandria, leaving 21 dead and 55 injured, January 1, 2011. [Xinhua]

Egypt's Health Ministry put the number of the injured at 43. Alexandria Governor Adel Labib said the injured had been rushed to five hospitals for treatment.Five have been discharged after receiving treatment, he added.

A car bomb went off at around 0:30 a.m. (2230 GMT Friday) Saturday at the All Saints Church while worshippers were leaving after they just ended a gathering for the New Year.

Egypt's Interior Ministry earlier said seven people were killed and 24 injured in the attack.

Egyptian President Hosni Mubarak has ordered a quick investigation into the bomb attack, official MENA news agency said Saturday.

The president "urged Egyptian Muslims and Christians to unite in face of terrorism and those who target Egypt's security and stability," it added.

Some police cars were burnt in clashes between Christians and police after the blast. Police used tear gas to disperse the crowds.

No group has so far claimed responsibility for the attack, which came about two months after the al-Qaida militant group in Iraq said in early November that Christians and their organizations have become "legitimate targets" after a two-day deadline expired for Egypt's Coptic churches to free two women allegedly held due to their conversion to Islam.

The Coptic church was one of the two which were attacked in April 2006 by a mentally-ill man who, with a knife, killed an elder worshipper.

Coptic Christians account for about ten percent of Egypt's total population of nearly 80 million. Tensions between Muslims and Coptics happen sometimes in Egypt for a number of reasons, including religious conversions.

Analysts believe the latest attack may fuel the tension between Muslims and Coptic Christians.

In late November, hundreds of Egyptian Coptic Christians clashed with police in Giza Governorate to protest the freeze of building a church, leaving one protester killed.

A few days before the November clash, Muslims set fire to some houses owned by the family of a Coptic man who was said to had an affair with a Muslim girl in southern Egypt.

The Egyptian government has been calling for and striving to achieve unity between the Muslim majority and the Coptics in the country.