jos, Nigeria: A suicide bomber blew his car up outside a church and gunmen opened fire on another service in Nigeria on Sunday, killing three people and wounding dozens in attacks claimed by Boko Haram.
The assaults were the latest in a series targeting churches in Africa's most populous nation and largest oil producer, with many of the previous attacks also claimed by the Islamist group, whose insurgency has killed hundreds.
A purported spokesman for Boko Haram claimed responsibility for Sunday's attacks and threatened further violence.
"We are responsible for the suicide attack on a church in Jos and also another attack on another church in Biu," the spokesman calling himself Abul Qaqa told reporters in the northeastern city of Maiduguri in a phone conference.
"We launched these attacks to prove the Nigerian security wrong and to debunk their claim that we have been weakened by the military crackdown," he said, speaking in the Hausa language common throughout Nigeria's north.
"The Nigerian state and Christians are our enemies and we will be launching attacks on the Nigerian state and its security apparatus as well as churches until we achieve our goal of establishing an Islamic state in place of the secular state."
The attacks took place at evangelical churches in the central city of Jos and the northeastern town of Biu, both of which have been hit before by violence blamed on Boko Haram.
"The suicide bomber did not drive into the church before the explosion. He was in front of it," police spokesman Abuh Emmanuel said of the Jos attack. "The church building collapsed entirely due to the intensity of the bombing."
Local government spokesman Pam Ayuba told AFP that two people plus the bomber died and 41 were wounded.
A reporter at the scene said angry Christian youths had assaulted local Muslims after the bombing.
The second attack killed at least one person and wounded several when gunmen opened fire during a service in Biu, Samson Bukar, the local Christian Association of Nigeria chairman, told AFP.
"One female worshipper was killed while several others were wounded, two of them critically. The gunmen escaped after the attack."
Boko Haram's insurgency has killed more than 1,000 people since mid-2009, especially in Nigeria's Muslim-dominated north.
Its attacks have grown increasingly sophisticated and have affected a wider area, spreading from their base in the northeast across the wider north and down to the capital Abuja, in the centre of the country.
It claimed responsibility for a suicide bombing of UN headquarters in Abuja in August which killed at least 25 people as well as a suicide attack on the Abuja office of one of the country's most prominent newspapers.
Its deadliest attack yet occurred in the northern city of Kano in January, when at least 185 people died in coordinated bombings and shootings.
Boko Haram also claimed a bomb attack at a church near the capital on Christmas day which killed at least 44 people.
The group has continually widened its targets, which have included security forces, churches and police headquarters in the capital.
Jos lies on the fault line between the Muslim-majority north and the Christian-dominated south.
In addition to the recent Boko Haram violence, repeated cycles of clashes and reprisal attacks in and around Jos have left several thousand people dead in recent years.
Biu is located in the northeastern state of Borno, which has been Boko Haram's base.
The group's mosque and headquarters were located in the Borno state capital of Maiduguri until a 2009 military assault destroyed them, an operation that left some 800 people dead.
Heavy-handed military crackdowns have so far failed to stop the group. Members are believed to have received training in northern Mali from Al-Qaeda's north African branch.
An attempt at dialogue between the government and Boko Haram in March collapsed when a mediator quit and a spokesman for what is seen as the group's main faction said they could not trust the government.
There have been conflicting claims in recent weeks over whether a new attempt at dialogue has got underway.