Fifty-two hostages and police were killed when an attempt by Iraqi security forces to free more than 100 Catholics held in a Baghdad church by al Qaeda-linked gunmen turned into a bloodbath, officials said on Monday.

Church officials described the attack, which began when gunmen seized the Our Lady of Salvation Church during Sunday mass, as the bloodiest against Iraq's Christians in the seven years of sectarian war that followed the 2003 US-led invasion.

The Islamic State of Iraq, the al Qaeda-affiliated group which claimed responsibility, also threatened the Christian church in Egypt over its treatment of women the group said the church was holding after they had converted to Islam.

Egypt condemned the threat to its Christian community, which makes up about 10 percent of the country's 78 million people. It beefed up security around churches.

Iraqi Human Rights Minister Wijdan Michael, a Christian, said at the scene of the Baghdad attack: "What happened was more than a catastrophic and tragic event. In my opinion, it is an attempt to force Iraqi Christians to leave Iraq and to empty Iraq of Christians."

Lieutenant General Hussein Kamal, a deputy interior minister, said 52 hostages and police were killed and 67 wounded in the incident, which ended with police storming the Assyrian Catholic church to free more than 100 hostages.

At least one bomb exploded at the start of the siege. Sporadic gunfire rang out for several hours over the Karrada neighbourhood near the heavily fortified Green Zone district where many embassies and government offices are located.

"The attackers were among children, armed with weapons," a federal police source who declined to be identified said of Sunday's rescue effort. "Most of the casualties were killed or wounded when the security forces raided the place."

Officials say some of the attackers blew up explosives vests or threw grenades during the raid. Security sources said many of the victims died in gunfights between police and insurgents.

Iraq's Christians, who once numbered 1.5 million out of a total Iraqi population of about 30 million, have frequently been targeted by militants since the invasion, with churches bombed and priests assassinated. Many have fled.

EGYPT TIGHTENS SECURITY

The Islamic State of Iraq said in a statement posted on Islamist websites the attack was on "the dirty den of idolatry" and gave the "church of Egypt, the head of infidels, 48 hours to make clear the condition of our sisters in Islam detained in the monasteries ... and announce their release in the media."

Islamist protesters in Egypt have accused the church of detaining two women, Camilia Shehata and Wafa Constantine, wives of Coptic priests, who reportedly converted to Islam.

Father Abdel Maseeh Baseet of the Coptic Orthodox Church said the two had not converted and were staying in monasteries for their safety. Egyptian Foreign Ministry spokesman Hossam Zaki denounced the Baghdad attack and the threat to Egypt.

The threat could aggravate communal tension in Egypt that is usually held in check but sometimes erupts into violence over land disputes, cross-faith relationships and conversions.

Egyptian security sources said extra forces were sent near churches in the capital and elsewhere. A witness in Nagaa Hamady, south of Cairo, said that after the threat six security trucks were moved near the church where six Christians and one Muslim policeman were killed in a drive-by shooting in January.

The United States condemned the attack on the Baghdad church, which was one of five in the Iraqi capital and city of Mosul hit in attacks in August 2004 that killed 12 people.

Source: Reuters