Cairo, Jan 1, (PTI): At least 21 people were killed and over 30 injured today in a massive car bomb attack at a packed church soon after the New Year's Mass in the Egyptian city of Alexandria, jolting the country's Christian community, the largest in the Middle East.

Nearly 1,000 Coptic Christians were present at the Saints Church in the Mediterranean port city of Alexandria for the Mass when the car bomb exploded, Father Mena Adel, a priest at the church, was quoted as saying by the media.

The service had just ended and worshippers were leaving the building when the car bomb went off in front of the church, about half-an-hour after midnight last night.

Egyptian authorities said 21 people were killed and over 30 others injured in the blast.

After the blast, an enraged Christian community members clashed with police and hurled stones at a nearby mosque, witnesses were quoted as saying.

No one has so far claimed responsibility for the attack on the Coptic church, which belongs to the Oriental Orthodox family of churches, but a group calling itself 'al-Qaeda in Iraq' has vowed to attack churches in the country.

The group threatened to attack Egyptian Copts if their church did not free two Christian women, who it alleged had been "imprisoned in their monasteries" for having converted to Islam. It earlier kidnapped Christian worshippers in the church of Lady of Salvation in the Iraqi capital of Baghdad.

Head of Al-Jumhurriya Centre for Security and Strategic Studies Samieh Sayf al-Yazal noted that this was the first time that a booby trapped car, a signature of al-Qaeda, was used in an attack in Egypt.

Another expert Rifat Sayid Ahmed said it was a direct message from al-Qaeda by which it wanted to instigate sectarian struggle within Egypt and depict it as a country where both sects cannot live together.

The Copts are the largest Christian community in the Middle East, who account for up to 10 per cent of Egypt's 80 million population.