MAPUTO (Reuters) - Mozambique put on Wednesday trial 189 people, including foreigners, accused of being involved in deadly Islamist attacks in a northern province.

Since October last year, more than 100 people have been killed, often by decapitation, in 40 separate attacks, in villages in Cabo Delgado - a province on the border with Tanzania where companies are developing one of the biggest gas finds in a decade.

The trial was held in the open penitentiary in Pemba, the provincial capital of Cabo Delgado, where hundreds of suspected militants including 50 from Tanzania are being detained.

The area is near one of the world’s biggest untapped offshore gas fields, and Anadarko Petroleum is seeking to raise $14 billion to $15 billion for a liquefied natural gas project in the region.

In June, President Filipe Nyusi vowed to be relentless and firm in neutralizing those responsible for the attacks.

He was quoted by state news agency AIM on Wednesday as saying he had instructed his security force in Cabo Delgado not kill them.

“If you catch these youths, don’t kill them. They are Mozambicans. They’ve been turned into instruments. They’ve been given orders by people who don’t want the development of this country and this province,” AIM quoted Nyusi as saying.

Security consultants and domestic media have described the attackers as members of Al-Sunna wa Jama’a, an unknown Islamist group. Residents have also referred to the attackers as “Al-Shabab”, although there are no known links to the Somali group of the same name.

Mozambique has no history of Islamist militancy and authorities have been reluctant to ascribe the attacks to Islamists. About 30 percent of Mozambique’s 30 million people are Roman Catholics, while 18 percent are Muslim.