About a dozen armed men attacked a southern Nigeria oil facility Wednesday, leaving two attackers dead in a fight with naval forces, police officials said.

Eleven men attacked the Oporoma station to try to shut down the facility, which is owned by a subsidiary of Royal Dutch Shell PLC, said Hafiz Ringim, police commissioner for Bayelsa state.

He said naval forces pushed back the men, and two of the assailants were killed in the fighting and one was captured.

No damage was reported to the flowstation, which connects oil pipelines. Shell officials were not immediately available for comment.

Ringim said the captured attacker told police the group mounted the assault to recover the rest of a ransom that was not fully paid after a hostage-taking last month.

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It was not immediately clear what kidnapping incident the attacker was referring to, although the same flowstation was attacked last month. Employees were held for two days and the facility was looted.

Ringim said the captured assailant said the group had only received $38,500 of a promised $300,000.

More than 60 foreigners have been kidnapped in Africa's largest oil producer since the beginning of the year, along with several times that number of Nigerians.

Separately, Ringim said kidnappers holding 35 Nigerian employees of Agip, a unit of Italian oil firm Eni SpA, had reduced their ransom demand to just over $30,000 from $75,000. The Agip employees have been held for over a week, though 13 managed to escape or were released.

Hostage-taking has become increasingly common in Nigeria's oil-rich Niger Delta, where most people live in abject poverty. Although tens of billions of dollars in oil revenues are extracted every year, massive government corruption means little of it is invested in infrastructure such as electricity, roads or education.

Analysts say a combination of corruption, frustration and the ready availability of arms means violence is likely to increase ahead of presidential elections in April. The country is the fifth-largest supplier of crude to the United States.