Nigerian authorities said 74-year-old Bridget Abahime, an ethnic Igbo trader and wife of a pastor, was "mobbed and extra-judicially murdered" on Thursday at a market in Kano, Nigeria's largest northern city.

Following reports that the woman was killed over a perceived insult on Prophet Muhammad, the northern chapter of the Christian Association of Nigeria said police are not doing enough to protect Christians and warned Saturday of a "looming religious crisis."

Such attacks have historically led to retaliations and sectarian violence.

"This barbarism must stop now," said the association's spokesman, Rev. John Hayab. He accused police of trying to cover up the killing.

Nigeria's national police chief Solomon Arase said Saturday that two suspects had been arrested, and appealed for calm on all sides. He added security forces were being deployed to Kano - the site of previous sectarian clashes - to prevent the incident from "degenerating into a major security threat."

Nigerian Muslim groups denounce killing

"The Muslim Rights Concern strongly condemns this gruesome murder," the group said in a statement. "It is preposterous, barbaric and unIslamic."

Meanwhile, Nigeria's President Mohammadu Buhari called the killing "utterly condemnable" and vowed that the perpetrators would be brought to justice.

"Let us ensure that we keep the peace, as justice will be done," Buhari said in a statement."Let us learn to respect each other's faith, so that we can know each other and live together in peace."

Nigeria's 170 million people are divided almost equally between Christians mainly in the south and Muslims predominantly in the north.

The northern region has been the scene of religious violence in the past. In one gruesome case in 1996, an Igbo Christian trader was beheaded by suspected Muslim youths who had accused him of desecrating the Koran.

His severed head was impaled on a spike and paraded around the city.

jar/jr (AP, AFP)