Amnesty International has urged Cameroon to investigate the death of 25 prisoners and disappearance of 130 people after raids by security forces, raising concern about possible abuses arising from a crackdown on Islamist Boko Haram militants.

Amnesty said that the Nigerian insurgent group had committed war crimes in neighbouring Northern Cameroon by having killed at least 380 civilians since the start of last year. In one attack in October, Boko Haram shot or slit the throats of at least 30 people in the border town of Ambchide, Amnesty said.

While providing protection to civilians in Northern Cameroon, security forces had committed serious human rights violations, Amnesty said. More than 1,000 suspects had been detained in raids by authorities on villages, in which homes were destroyed and civilians killed, it said.

Amnesty highlighted a raid by security forces in December in the villages of Magdeme and Double, in which 70 buildings were burnt down and at least eight people killed, including a 7-year-old child, according to residents.

At least, 200 men and boys were detained in the raid. The government has said that 25 died in their first night of detention from asphyxiation, but Amnesty said that another 130 remain missing.

Steve Cockburn, Amnesty's deputy regional director, appealed for Cameroonian authorities to launch an independent, impartial and rigorous investigation into the killings, disappearances and detentions.

“We can't have a situation where the population is scared of the people who are protecting them," he told Reuters. "What that means concretely is a change of tactics to avoid the type of operation that leads to the mass arrests we have seen." Amnesty found that overcrowding, lack of sanitation and inadequate health care in a prison in Northern Cameroon's main town of Maroua led to the death of at least 40 prisoners between March and May. The rights group called for a rapid improvement in conditions of detention.

Cockburn voiced concern that an offensive against Boko Haram due to be launched this year by an 8,700-strong regional force -- composed of troops from Nigeria, Cameroon, Chad, Niger and Benin -- could lead to more abuses.

"That brings with it the risk of future human rights violations unless there are further measures taken to prevent the sort of mass arrests and other violations that we have seen over the last months," he said.