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By Austin Ekeinde

PORT HARCOURT, Nigeria, Nov 7 (Reuters) - Gunmen in speedboats attacked the Nigerian military at an oil flow station operated by U.S. energy firm Chevron <CVX.N> late on Thursday but the facility was not affected, the military said on Friday.

"Last night, some men in speedboats attacked our men at Robert-Kiri flow station. In the shoot-out there were fatalities. We lost one man, a naval personnel," said Lieutenant Colonel Sagir Musa, a military spokesman in the Niger Delta.

"The attack did not affect the Chevron facility," he added. He said it was not clear who was responsible.

Chevron was not immediately available for comment.

Musa said several attackers had been killed in the shoot-out, which took place near the border between Rivers and Bayelsa states in the Niger Delta. A private security source working in the oil industry said several navy officials died.

Militants who say they are fighting for a fairer share of the wealth generated in the Niger Delta, home to Africa's biggest oil and gas industry, have bombed pipelines and oil platforms in recent years to push their demands.

But the line between militancy and criminality is blurred.

Networks of armed gangs have taken advantage of the breakdown in law and order to steal industrial quantities of crude oil -- known locally as "bunkering" -- part of an illegal international trade worth millions of dollars a day.

The unrest has cut oil output from the world's eighth biggest exporter by around a fifth. Nigeria is pumping just under 2 million barrels per day (bpd), well below its capacity of 3 million bpd, largely because of the insecurity.

Gunmen in speedboats trying to secure safe passage for crude oil thieves killed a civilian during a gun battle with the Nigerian security forces in Bayelsa in the western Niger Delta late on Wednesday, the military said on Thursday.

The attack was a rare spill-over of violence which has been concentrated in Rivers state in recent months. (Writing by Nick Tattersall; Editing by Randy Fabi)

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