The President of Open Doors USA has asked for prayers after Christians were apparently targeted in bomb attacks in Baghdad on Christmas Day.

At least 37 people were killed, most of them Christians, in two separate bomb attacks.

One bomb exploded outside of the St John's Catholic Church while worshippers were leaving a Christmas Day service, killing at least 26.

Another bomb ripped through an outside market in a Christian neighbourhood, killing at least 11.

Around 60 people were injured in the attacks.

One pastor who cannot be named for security reasons told Open Doors recently that "churches are targets for terrorists, especially on Christmas Day. Many Christians stay home because they are too afraid".

An Open Doors field worker said in an earlier report: "We received documents and threats stating that the aim of Islamist insurgents is to make Iraq a 'Muslim only' country. They want Christians out."

Hundreds of thousands of Christians have left Iraq in the last decade because of violence and persecution. While the Christian population was around 1.2 million in the early 1990s, today there are only an estimated 330,000 remaining.

The extent of the violence against Iraqi Christians is so bad that the country ranks fourth in the Open Doors World Watch List of countries with the worst persecution of Christians.

Dr David Curry, president/CEO of Open Doors USA, has appealed to Christians in the West to pray fervently for all the Christians affected by the killings.

"There is a concerted effort by extremists to drive Christians out of the Middle East," he said. "Iraq not only is a hostile, volatile environment in general, but often the violence is directed specifically towards Christians. As a result, one of our field workers said that if the exodus of Christians from Iraq continues at the current pace, it is possible there could be no Christians left in Iraq by 2020.

"Only the power of prayer is going to improve the conditions for believers in Iraq and countries such as Syria and Iran. Pray that the families of the victims will feel the embrace of Jesus. Pray that the government of Iraq will do more to protect people of all faiths. And pray that in 2014 Christians will be able to worship the Lord in peace and freedom."

There have been similar attacks on Christians around Christmas time elsewhere in the world. In the last three years, the Two Saints Coptic Church in Alexandria, in Egypt, was bombed on New Year's Eve, and Christians in Nigeria also fell victim to deadly Christmas bombings.

Curry said attacks on Christians during Christmas and New Year's Eve had become a "very disturbing trend".

The Open Doors ministry in Iraq includes trauma counseling, biblical training for church leaders and Muslim Background Believers, distribution of Bibles and Christian literature, community development projects and working with Internally Displaced Peoples (IDPs) in northern Iraq.