LAGOS (Reuters) - The Nigerian military repelled an attack by gunmen in speedboats yesterday close to the Escravos crude oil export terminal, a major facility in the western Niger Delta operated by US energy giant Chevron.

The attack was the latest sign that unrest which has recently been largely contained in Rivers state in the eastern delta was threatening to spill back into neighbouring states.

"They came in about 10 speedboats. The attack has been repelled," Brigadier General Wuyep Rimtip, a commander of the joint military taskforce in the western Niger Delta, told Reuters, adding two of the attackers' boats had been sunk.

A Chevron spokesman said operations were normal at the Escravos terminal, situated in Delta state, and that no employees were hurt in the incident.

Rimtip said the attack was believed to have been carried out by a criminal network involved in the theft of crude oil — a practice known locally as "bunkering" — in retaliation for the recent seizure of a vessel used in the illegal trade.

He said the gunmen were thought to be part of a gang responsible for hijacking the MV Thou Galaxy cargo ship and its crew on Sunday as it sailed towards Warri in Delta state. The vessel and those on board were released on Monday.

No group has claimed responsibility for the hijacking or for the attack at Escravos.

Insecurity in the Niger Delta, home to Africa's biggest oil and gas industry, has slashed a fifth of the Opec member's oil production since early 2006. The world's eighth biggest exporter currently is pumping around two million barrels per day.