At least six navy personnel were killed in a gun battle between two rival gangs in southern Nigeria's oil-rich Bayelsa state, one of their colleagues said Friday.

"Six of our men on a mission to keep the peace were shot dead by the warring youths in Nembe yesterday (Thursday)," he told AFP in the Yenagoa hospital where he was undergoing treatment for a gunshot wound.

He said some of the gang members also died in the violence, which appeared to have been sparked by a dispute over local politics.

Navy authorities were not immediately available to confirm the incident.

Dozens of Nigerian military personnel have been killed in the volatile Niger Delta following an upsurge in unrest in the past three years.

Attack on Chevron in Nigeria kills navy sailor: military
Armed men attacked an oil facility operated by US giant Chevron in southern Nigeria overnight, killing a Nigerian navy sailor, a military spokesman said Friday.

"The militants came in eight speed boats to attack the Robert-Kiri flowstation operated by Chevron at around 2.30 am. The military repelled the attack and sank two of the boats with all the occupants," Lieutenant Colonel Musa Sagir told AFP.

"Unfortunately we lost a navy rating in the incident. But the Chevron facility was secured," he added.

Sagir said no group had claimed responsibility for the attack, the latest to hit oil-rich Nigeria in recent months.

Since January 2006, militant attacks have cut Nigeria's oil output by more than one quarter. Production currently stands at between 1.8 and two million barrels a day (bpd) against 2.6 million bpd two years ago.

Nigeria was Africa's largest oil producer before it was overtaken in April by Angola, according to OPEC figures.

In the past three years, Nigeria has also seen a spate of kidnappings both of local and foreign oil workers and of relatives of prominent politicians, often by criminal gangs seeking a ransom, but sometimes also for political ends.