– Cameroon sent additional soldiers to the north after the government said it suspects Boko Haram kidnapped the wife of Deputy Premier Amadou Ali, the highest profile attack by the Islamist militants outside Nigeria.

Gunmen attacked Ali's home and killed an unknown number of people and abducted Agnes Francoise Ali and others, Minister of Communications Issa Tchiroma said by phone in Yaoundé on Sunday.

"Since May, Cameroon has moved from quiet containment of Boko Haram to active confrontation with the group," Freedom Onuoha, a research fellow at the National Defence College in Abuja, Nigeria, said by phone on Sunday. "I don't expect them to kill such a high-value target, but rather to rake in enough money to help fund their operations."

Boko Haram has been fighting security forces in neighboring Nigeria for the past five years to impose Islamic law on Africa's biggest economy and oil producer. The group claimed responsibility for the worst bombing in Nigeria's capital in April and has killed more than 2,500 people in the first half of the year.

Cameroonian President Paul Biya sent more than 1,000 troops to the border with Nigeria as Boko Haram intensified cross-border attacks into Cameroon this year. Nigeria, Cameroon, Chad and Niger agreed at a May conference in Paris to set up a joint force to patrol the border areas, as the Islamists continue to expand their reach in the region.

In April, the group abducted more than 200 schoolgirls from Chibok, a Nigerian town in the northeastern state of Borno, close to the border with Cameroon. The group's name means "western education is a sin" in the Hausa language. Most of the schoolgirls are still missing.

Others abducted last year, but later freed, include a Canadian nun, a French priest and two Italian priests. Ten Chinese construction workers kidnapped in Cameroon in May remain in captivity.

Tens of thousands of northern Nigerians have fled into Cameroon in the last year.

In northern Nigeria's biggest city, Kano, an attack on a church Sunday by unknown assailants left five people dead and others wounded. No group immediately claimed responsibility.

The Los Angeles Times contributed to this report.