Church leaders have expressed their sorrow over the attack on a church in Iraq that left around 58 people dead.
Pope Benedict XVI denounced the attack on the Our Lady of Salvation Church in Baghdad as "absurd … ferocious violence."
Gunmen linked to al-Qaeda entered the church on Sunday and took the congregation hostage as they were gathered for evening Mass.
Priests, women and children were among those killed when the gunmen opened fire as security forces stormed the church in a bid to free them.
The General Secretary of the World Council of Churches, the Rev. Dr. Olav Fykse Tveit, also condemned the attack.
"The World Council of Churches strongly condemns the criminal act of terror that took place on Sunday in the Sayyidat al-Najat Church in Baghdad and expresses its deep sympathy and solidarity with those who lost their loved ones and pray for a speedy recovery for the injured," he said.
The Moderator of the General Assembly of the Church of Scotland, the Rt. Rev. John Christie, said it was "impossible to comprehend the shocking tragedy."
"I can find no words which adequately offer solace for the families bereaved in such tragic circumstances nor indeed any words which will offer any adequate comfort for those who survived this dreadful incident," he said. "All we can do in such circumstances is to commend those who have been bereaved and those who have survived to the love and grace and peace of Jesus Christ and assure them of the prayers and thoughts of us all."
A statement posted on a website run by the Sunni militant group Islamic State of Iraq reportedly warned of attacks on Iraqi Christians and made demands for the release of two women converts to Islam the group said were being held against their will by the Coptic Church in Egypt.
Witnesses report having heard a loud explosion outside the church on Sunday, as around 100 people were taking part in Mass inside.
Sunday's attack is the deadliest on an Iraqi church in the last few years. In February, at least eight Christians were killed in a string of attacks on churches in Mosul, in the north of the country.
In April 2008, Assyrian Orthodox priest Fr Adel Youssef was killed by unknown gunmen, not long after the kidnapping of Chaldean Catholic Archbishop Faraj Rahh. His body had been found a couple of weeks after his disappearance.
In January 2008, dozens of Christians died when Chaldean and Assyrian churches in Mosul, Kirkuk and Baghdad were bombed by militants.
Dr. Tveit said the WCC was "deeply troubled" by the "continuous suffering" of Christians in Iraq and that it would continue to stand in solidarity with churches experiencing "hatred and aggression" in the country.
"This is not the first time that such attacks have targeted Christian communities in Iraq," he said.
"All those responsible need to be brought to justice, and governmental authorities should take their responsibility to bring safety and security to all citizens and particularly to those in vulnerable situation."