A bomb factory exploded Monday in the central Nigerian city of Kaduna, a day after members of Boko Haram, a radical Islamist group, were arrested in the northern city of Kano.

The explosion at a house outside the National Eye Centre. The house was being used to manufacture explosive devices, police said.

Explosives found at the scene were similar to those used to destroy market stalls in Kaduna two weeks ago. Neighbouring houses were destroyed in the blast.

Fears were raised of revenge attacks after Nigerian police announced the arrests of key members of Boko Haram Sunday. They include Mohammed Aliyu, believed to be one of the leaders of the group.

Aliyu was arrested at his home in Kano Sunday, during a shoot-out between police and suspected members of the group. Seven people were killed in the exchange, including two policemen and three members of Boko Haram, the group said in a statement Monday.

Fourteen suspected members of Boko Haram, the group founded under the motto "Western education is a sin," have been detained in recent days. On Saturday, police seized a bomb-making factory in Maiduguri, the group's official base.

Recent attacks by suspected members of the group have targeted markets, wedding ceremonies and a school in Nigeria's arid north.

The group claimed responsibility for an attack on the UN's Nigerian headquarters in August, which left 23 people dead.