(BBC) -- The Iraqi government says it had no choice but to storm a Catholic church in Baghdad in which gunmen were holding dozens of people hostage.
Defence Minister Abdul-Qadr al-Obeidi said the gunmen had threatened to kill all their captives.
At least 52 people were killed as security forces stormed the church, attempting to free the hostages.
Deputy Interior Minister Maj Gen Hussein Kamal said six attackers also died in the fighting.
Other sources, however, have said the overall death toll was lower. The number of wounded is put at between 56 and 62 - many of them women.
Witnesses said the interior of the church resembled a battlefield.
Throughout Monday mourners have been carrying coffins from the church and loading them on to vehicles taking them to a morgue. Most victims are to be buried on Tuesday. 'Impossible to wait'
The gunmen had reportedly demanded the release of jailed al-Qaeda militants.
A statement was posted on a militant website allegedly run by the Islamic State of Iraq, a Sunni militant umbrella group to which al-Qaeda in Iraq belongs, claiming responsibility for the attack.
The statement reportedly said Iraqi Christians would be "exterminated" if Muslim women in Egypt were not freed. It specifically mentioned two women in Egypt who radicals believe are being held against their will after converting to Islam.
Iraqi Defence Minister Abdul-Qadr al-Obeidi said security forces approached the building at ground level and from the air.
"We took a decision to launch a land offensive, and in addition an airdrop, because it was impossible to wait - the terrorists were planning to kill a large number of our brothers, the Christians who were at Mass," said Mr Obeidi.
"So the operation was successfully done. All terrorists were killed. And we now have other suspects in detention."
Witnesses say they saw US troops on the ground and US military helicopters hovering above the scene, but the extent of their involvement is not yet clear.
Younadim Kanna, a Christian Iraqi MP, said the government had failed to protect its citizens, but added that the Christian community would not be intimidated by violence.
"Despite all of these terrorist attacks against the Christians, we are determined not to leave our country," he said. 'Absurd violence'
Residents of Baghdad's affluent Karada district, where the attack took place, first heard a loud explosion at about 1700 (1400 GMT) on Sunday, believed to have been a car bomb.
About 100 people were inside Our Lady of Salvation for an evening Mass at the time.
The blast was followed by gunfire as a group of armed men attacked the Iraq Stock Exchange, police said, and then took over the Catholic church just across the road, clashing with guards and killing some.
It seems the church was the attackers' real target, says the BBC's Jim Muir in Baghdad.
One eyewitness, who was inside the church, said the gunmen "came into the prayer hall and immediately killed the priest". The witness, who declined to give his name, said worshippers were beaten and herded into an inner hall.
The militants made contact with authorities by mobile phone, demanding the release of al-Qaeda prisoners and also of a number of Muslim women they insisted were being held prisoner by the Coptic Church in Egypt.
But the discussions got nowhere, our correspondent says, and the security forces stormed the church.
Witnesses nearby said they then heard two explosions from inside the church and more shooting. The gunmen reportedly threw grenades and detonated suicide vests.
Pope Benedict XVI denounced the attack as he gave a holiday blessing on Monday.
Minority Rights Group International (MRG) said religious and ethnic minorities in Iraq faced unprecedented levels of violence.
"The security situation for Christians and other religious minorities in Iraq has become critical,' said executive director Mark Lattimer.
"The safety of minorities must now become an urgent priority for the Iraqi government, with security measures planned in full co-operation with community leaders."
Many churches have been bombed in recent years - including Our Lady of Salvation in August 2004 - and priests kidnapped and killed, but there has never been a prolonged hostage situation like this before, our correspondent says.
Christians - many from from ancient denominations - have been leaving Iraq in droves since the US-led invasion in 2003, and about 600,000 remain.