Nigeria's military says gunmen in speedboats have killed one navy sailor during an attack on an oil flow station operated by the U.S. energy firm Chevron in the oil-rich Niger Delta region.

The military says it repelled the attack at the Robert-Kiri flow station, near Rivers and Bayelsa states, earlier Friday. A spokesman was quoted as saying the attack did not affect the Chevron station.

He was also quoted as saying several militants had been killed.  The information could not be independently verified.

On Wednesday, a Lebanese engineer kidnapped in the main Niger Delta city of Port Harcourt earlier in the week was released unharmed.

Hundreds of foreigners have been kidnapped in recent years in the Niger Delta, while attacks on oil installations happen frequently.  Militants say they want a better share of oil wealth for the local population, but the government says they are criminals looking for ransom money.

Nigeria is one of the world's top 10 exporters of crude oil in the world, but poverty remains rife in oil-producing areas.

Some information for this report was provided by AFP, AP and Reuters.