At least 15 people were killed in two attacks blamed on Boko Haram in northern Cameroon, with the wife of the country's deputy prime minister among a dozen people reportedly kidnapped, a security source said on Monday.

The death toll from the two reportedly simultaneous raids on Sunday by Nigerian Islamic extremists on the palace of the Sultan Kolofata, and the nearby home of one of the country's most senior politicians, deputy premier Amadou Ali, rose on Monday from six to at least 15.

The sultan, Seiny Boukar Lamine, his wife and their five children were among the hostages, a government spokesman confirmed.

Two gendarmes and a member of the Cameroonian army's elite Rapid Intervention Battalion (BIR) were among the dead, a gendarme involved in the follow-up operation against the terrorists told AFP.

"We listed around 15 dead, including two gendarmes and a soldier from the BIR," he said. "About a dozen people were kidnapped." Around 200 militants were involved in the raids, Cameroon's minister of communications, Issa Tchiroma Bakary, told local TV on Sunday.

The attacks come after Cameroon stepped up its fight against Boko Haram in the wake of the international outcry over the kidnapping of more than 200 Nigerian schoolgirls on April 14.

"It's a big blow, the country is in a state of shock," a journalist on national television said. He claimed that some of the victims had been "burned alive". Boko Haram has long considered the northern Kolofata region, close to the Nigerian border, as a haven for its activities, and as a route for smuggling weapons.

Asked about the fate of the hostages, the gendarmerie source said "there are reasons to be optimistic and that maybe we will have a happy ending rather quickly, but at this moment that is not the case."

The dramatic raids follow the deaths of several Cameroonian soldiers and gendarmes killed in two attacks blamed on the militants on Thursday and Friday.