Nigeria's main militant group says it has destroyed an oil pipeline belonging to the US company Chevron in the country's southern Delta region.

"A major gas pipeline manifold and another major crude oil pipeline belonging to Chevron JV recently repaired at a sum of over $US56 million ($A68.39 million) were both blown up," the Movement for the Emancipation of the Niger Delta (MEND) said in a statement on Friday.

It warned that its fighters were heading to the Chevron tank farm in Escravos and urged staff to flee.

A Chevron spokesman declined to comment while it was investigating Friday's claimed attack.

MEND, which has staged numerous attacks on international oil facilities in southern Nigeria as part of its campaign to get what it calls a fairer distribution of the region's oil wealth to local people, declared last weekend a new campaign against oil companies.

The group later claimed responsibility for a fire at a Chevron pumping station.

A MEND attack last month knocked out a Chevron pipeline, forcing a 100,000 barrel-per-day oil output cut, over one quarter of the company's Nigerian production.

On Friday the group released a British oil sector worker who had been held for nine months.Nigeria's oil production has been cut by more than a quarter because of the militant campaign over the past three years, allowing Angola to catch up and compete with it for the position of Africa's top oil producer.

AFP LAGOS