The Nigerian navy has killed 12 suspected pirates and rescued a hijacked vessel laden with fuel in the country’s oil-producing Niger Delta region, authorities said Tuesday.

The Nigerian navy has killed 12 suspected pirates and rescued a hijacked vessel laden with fuel in the country's oil-producing Niger Delta region, authorities said Tuesday.

It said naval gunboats were deployed to free the St. Kitts and Nevis-flagged MT Norte which was reported to have been seized by 16 pirates off Nigerian waters last week.

The navy said it engaged the pirates in a gunbattle when they attempted to escape in a speedboat after disembarking from the vessel around the Forcados area on Saturday night.

"Efforts to get the hijackers to stop and surrender proved abortive as they engaged NNS Badagry in a gunbattle," it said.

The gunbattle between NNS Badagry and the pirates lasted for about 30 minutes after which they were over-powered... and four of them surrendered by raising up their hands," it said.

The navy said after capturing the boat, "it was discovered that most of the pirates were killed in the crossfire," while a cache of arms and ammunitions was recovered.

The MT Norte was carrying some 17,000 tonnes of petrol.

Hijackings of tankers with the aim of stealing fuel cargo has been rife off the coast of Nigeria, Africa's largest oil producer, but the problem has recently spread to other areas of the region.

The Gulf of Guinea, which includes the waters off Benin, Nigeria and Togo, has been an emerging piracy hub.

Such incidents however rarely result in authorities firing upon pirates.

Crude oil theft has also been a major problem in Nigeria, with thieves tapping pipelines and siphoning off oil before loading it aboard waiting vessels.