Yenagoa - Gunmen on a speedboat in the oil-producing south killed four policemen and kidnapped six employees of the Agip energy firm, in the latest unrest to hit the restive region, the security forces said Tuesday.
The attack happened on Friday in the Nembe Creek area of Bayelsa state, which was one of the most violent regions of the delta at the height of an insurgency that formally ended in 2009.
"Four policemen who were escorting a boat were attacked and killed. Six oil workers were abducted in the incident," said Mustapha Anka, spokesman for the military's Joint Task Force in the region.
National police spokesman Emmanuel Ojukwu told AFP that three officers were killed but multiple reports from the region put the death toll at four.
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A security source in the delta identified the hostages as employees of the Nigerian subsidiary of the Italian energy firm Agip, which is controlled by ENI, one of the world's largest oil companies.
Criminality, especially ransom kidnappings, has persisted in the delta since a 2009 amnesty deal with militant leaders ended the formal rebellion.
But there is widespread concern over escalating violence in the region, with the amnesty deal set to expire next year.
Officially, the peace deal offered job training and other benefits to militants who voluntarily gave up their arms.
But experts say that in practice the deal amounted to massive cash payouts to gang leaders who could resume fighting if the money is shut off.
The Niger Delta, home to Africa's largest oil industry, is made up of a network of rivers and creeks.
Criminal groups have a track record of speeding around on small boats and launching gun attacks on the security forces and oil workers.
Both foreign and Nigerian hostages have typically been released following a ransom payment.