"We are responsible for the suicide attack on a church in Jos and also another attack on another church in Biu," a spokesman for the group, Abul Qaqa, is said to have told reporters in the northeastern city of Maiduguri over the phone.

The group was responsible for recent terrorist attacks, in which six people were killed and dozens injured after a suicide bomber detonated explosives outside a church in Jos and other Boko Haram gunmen opened fire at worshippers in a church in Biu.

"We launched these attacks to prove the Nigerian security wrong and to debunk their claim that we have been weakened by the military crackdown," the spokesman added, referring to the Nigerian military fighting back against the group in recent times, managing to kill 19 terrorist gunmen in a shootout last week in the cities of Kano and Maiduguri.

Nigeria, which is largely divided along geographical and religious lines, with most Christians concentrated in the South and Muslims living in the North, has been unable to contain the violence aimed at churches. Boko Haram has killed hundreds of Christians throughout the past year, and despite President Goodluck Jonathan's promise to do all he can to push back against the group, they are still very active in the country.

"We will crush them. We will begin from tonight to take different measures, different approach in fighting Boko Haram and we must weed them out from the society," Jonathan said earlier this year.

The Islamic extremists have been increasingly vocal about their activities, and even warned journalists about forgetting to include their statements in stories covering their attacks.

"We are keeping tabs on all comments being made about us ... Let no one make any entreaty to us when we perfect our plan and start our operation, especially against journalists," Boko Haram said in a statement earlier this month.

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