Bomb attacks on churches during Christmas services, including one outside the capital, have killed at least 28 people in Nigeria amid spiralling violence claimed by an Islamist group.

A purported spokesman for Islamist group Boko Haram claimed responsibility for a bombing of the church outside the Nigerian capital and other violence in recent days that has stoked fear and anger in Africa's most populous nation.

Authorities have been seemingly unable to stop the attacks despite heavy-handed military crackdowns and claims of arrests of Boko Haram members.

The area around the scene of the blast outside the capital Abuja, which killed at least 27, degenerated into chaos after the explosion, with angry youths starting fires and threatening to attack a nearby police station.

Police shot into the air to disperse them and closed a major highway. Emergency officials called for more ambulances as rescuers sought to evacuate the dead and wounded, and calm later returned to the area.

In a swift response, a Vatican spokesman condemned that attack as an act of 'blind hatred' which sought 'to arouse and feed even more hatred and confusion'.

A bomb blast later hit outside an evangelical church hundreds of miles away in the central city of Jos, killing a policeman, according to a spokesman for the governor.

Another explosion targeted a church in the northeastern area of Gadaka on Christmas Eve, but no one was reported killed, while two other blasts hit the northeastern city of Damaturu on Christmas Day, including a suspected suicide bombing.

Emergency officials initially said the blast outside Abuja happened in the church, but later said it occurred near it, with the impact felt inside the church, which was also damaged.

Holes could be seen in the wall of the St. Theresa Catholic Church in Madalla and the roof was badly damaged. What looked to be blood was splashed on the outside of the wall.

"The officials who counted them told me that 27 people died," Father Christopher Barde said, adding that the explosion happened as the Christmas morning service was ending.

"As I reached the last entrance, some people met me for blessings and suddenly I heard a bomb blast. It was really terrible."

Nigerian police affairs minister Caleb Olubolade visited the scene .

"This is like an internal war against the country," he said.

"So we have to really live up to it and face it squarely."

A purported spokesman for Boko Haram claimed responsibility for the violence.

"We are responsible for all the attacks in the past few days, including today's bombing of the church in Madalla," Abul Qaqa told AFP by phone.

"We will continue to launch such attacks throughout the north in the next few days."

Boko Haram has claimed responsibility for scores of attacks in Nigeria, including the August suicide bombing of UN headquarters in Abuja that killed at least 24 people. There have been a number of attacks in Suleija area, also outside Abuja.

A string of bomb blasts in the central city of Jos on Christmas Eve 2010 were claimed by Boko Haram.

In recent days in three cities in the northeast, where most of the violence attributed to Boko Haram has occurred, attacks blamed on the sect followed by a heavy military crackdown killed up to 100 people, authorities and a rights group have said.

The chief of army staff, Lt. Gen. Azubuike Ihejirika, was quoted by local media as saying soldiers killed 59 Boko Haram members in Damaturu. Shootouts had taken place on Thursday and Friday.

Others said the total death toll on all sides - authorities, extremists and civilians - could be as high as 100.

A purported spokesman for Boko Haram claimed responsibility for the initial violence in the three northeastern cities, saying they were revenge for a brutal military assault against the sect in 2009.

Violence blamed on the sect has steadily worsened in recent months, with bomb blasts becoming more frequent and increasingly sophisticated and death tolls climbing.

The attacks have continued despite well publicised raids on so-called bomb factories and arrests of a number of alleged Boko Haram members by authorities.

There has been intense speculation over whether Boko Haram has formed links with outside extremist groups, including Al-Qaeda's north African branch.

The group is believed to have a number of factions with varying aims.

It launched an uprising in 2009 that was put down by a brutal military assault which left some 800 dead as well as its mosque and headquarters in the northeastern city of Maiduguri in ruins.

It went dormant for about a year before re-emerging in 2010 with a series of assassinations.