Christians are demanding that authorities do more to protect them after a woman was stabbed to death for allegedly insulting the Prophet Muhammad in Nigeria's mainly Muslim north.

Nigeria's police chief said Saturday that two suspects have been arrested in Thursday's killing of a middle-aged petty trader, Bridget Abihime, who allegedly said the Prophet Muhammad was not important.

But the Christian Association of Nigeria said police are not doing enough to protect Christians and warned Saturday of a "looming religious crisis." In the past, such attacks have led to retaliation and sectarian violence.

Most Christians and Muslims live side-by-side peacefully in Nigeria but tensions are high in the north and especially the northeast where Boko Haram's near 7-year-old Islamic insurgency has killed about 20,000 people and suicide bombings keep people in fear. Kano has suffered several such attacks.