KANO, Nigeria — Witnesses say a woman blew herself up at a petrol station in northern Nigeria, killing at least three people.

Monday's attack in Kano comes amid other bombings, and was the second by a female suicide bomber in two days.

Tijjani Isa said he saw the woman standing in line to buy kerosene for cooking before she set off the bomb.

Police say a 15-year-old female suicide bomber detonated a bomb Sunday near a university. Five others were killed in a church bombing, and a third bomb was discovered at a mosque before it detonated.

Police Commissioner Aderenle Shinaba said three suspected Boko Haram militants were arrested immediately after the church bombing. Boko Haram has killed thousands of people in five years of insurgency, including hundreds of children.