Nigeria's security forces clashed with militants, Wednesday, heightening security concerns in the volatile Niger Delta. Militants are continuing their occupation of two facilities in the region.

Police commissioner for Bayelsa state, Hafiz Ringim says two militants may have been killed and another arrested, in Wednesday's clash.

"This morning, there was an encounter between the navy and another group of militants at the Okoromar area. Two militants were said to have been killed, but one I can assure you has been arrested and is with the police right now," he said.

The Nigerian military has stepped up security patrols in the region following a recent threat by a militant group to attack oil facilities.

The Niger Delta, a vast wetland region which accounts for most of Nigeria's petroleum  wealth, is caught in a cycle of violence driven by poverty, corruption and lawlessness.

Militants are continuing their occupation of two flow stations in the region. Scores of Nigerian workers and soldiers are reported being held by militants who invaded the facilities in the past week to press demands for benefits.

The government's refusal to pay ransom seems to be stalling negotiations to lift the siege, as local police chief Ringim explains to VOA.

"They are asking for four million naira [about $30,000] before they release everybody," he explained. "The government is refusing to give them four million naira because, if we give them four million naira, they will move to another flow station. We are still discussing."

The Movement for the Emancipation of the Niger Delta, a militant group whose February attacks forced a drastic cut in oil production, said recently it intends to resume attacks and take more hostages.

Nigeria, the world's eighth-largest exporter of oil, has lost 500,000 barrels in daily crude production since February.