Nigeria on Monday probed a wave of Christmas Day bomb attacks that killed at least 40 and was blamed on Islamists, including one blast that ripped through a crowd of worshippers exiting mass.
The government blamed Islamist sect Boko Haram for three attacks on Sunday, including bomb explosions at two churches — the deadliest as Christmas mass ended near the capital Abuja — and a suicide attack in the northeast.
A third church was targeted in the northeast on Christmas Eve, but no one was reported killed. Residents reported another explosion near a church in the northeastern city of Maiduguri late Sunday, but an army spokesman denied it.
The attack at St. Theresa Catholic Church in Madalla outside Abuja killed at least 35 and left a gruesome scene, with rescuers picking up body parts and putting them in plastic bags while emergency workers pleaded for ambulances.
Some of the wounded, including one man whose entrails protruded from his body, ran toward a priest for final blessings.
The attacks drew widespread condemnation, including from UN chief Ban Ki-moon, the United States and Britain.
Authorities and officials pledged to bring the attackers to justice, but the government in Africa's most populous nation has so far been unable to stop the Islamists, whose attacks have grown increasingly sophisticated and deadly.
President Goodluck Jonathan condemned the violence and his national security adviser called it "unnecessary bloodletting by a group whose objectives are not in consonance with any genuine religious tenants."
While the government blamed Boko Haram and a purported spokesman for the sect claimed responsibility for the violence, conflicting accounts emerged of both the investigation and the attack in Madalla.
A spokesman for police in Niger state, where Madalla is located, said on Monday that authorities had not yet determined who was behind the attack.
"We are looking beyond Boko Haram because other people bent on destabilizing the government might be doing these things in the name of Boko Haram," said Richard Oguche.
Describing the attack, National Security Adviser Owoye Azazi said attackers threw improvised explosive devices from a moving vehicle in Madalla, adding that "two of the criminals had been apprehended, caught in action."
Oguche said no one was arrested and the blast occurred after a minibus pulled up near the church. He added that three police officers were among those killed.
"It was just about the time people were leaving the church and there was a (minibus)," said Oguche.
"There were three police officers at the gate and they were trying to prevent those people from coming in. There was an argument and in the process the thing exploded."
The attack sparked further chaos in the area, with angry youths setting fires and threatening to rush a police station. Police fired into the air to disperse them and cleared a road for rescue workers.
Other explosions occurred in the central city of Jos, where a church was targeted and policeman was killed in a resulting shootout, and in the northeastern city of Damaturu, where authorities have clashed with Islamists in recent days.
A suicide blast occurred in Damaturu when the bomber sought to ram into a military convoy in front of a secret police office, killing himself and three security agents. Sporadic gunfire broke out in the city on Sunday afternoon.
In Damaturu on Monday, hundreds of residents were seeking to flee, lining up at taxi and bus stands, seeking to take advantage of the momentary calm in the tense and violence-torn city.
Boko Haram had also claimed responsibility for a deadly wave of attacks in the Jos region on Christmas Eve last year.
Violence blamed on Boko Haram has steadily worsened in recent months, with bomb blasts becoming more frequent and increasingly sophisticated and death tolls climbing.
There has been intense speculation over whether Boko Haram has links with outside extremist groups, including al-Qaida's north African branch. It is believed to have a number of factions with varying aims.
Nigeria, Africa's largest oil producer and most populous nation with 160 million people, is roughly divided between a mainly Muslim north and predominately Christian south.