Nigerian gunmen attack oil boats

Security sources told the BBC the militants had used the gun from a navy boat they had recently destroyed mounted on their own vessel.

Meanwhile, the mother of a local politician has been freed after being kidnapped 10 days ago, officials say.

Such attacks and kidnappings have cut Nigeria's oil output by 25%.

The Rivers State police chief says that three people were killed in the attack on two boats on their way from Bonny Island and the region's main city, Port Harcourt.

A security source added that a policeman had also been killed in the clash.

He said that the militants had escaped with the guns of five policemen travelling on the boats.

They also made off with the valuables of other passengers.

Oil giant Shell has its main Nigeria terminal on Bonny Island - two hours by boat from Port Harcourt.

Relatives targeted

Bayelsa State government spokesman Ebimo Anungo denied that a ransom had been paid to secure the release of the elderly mother of the speaker of the state parliament, Werenipre Seibaguru.

The AFP news agency reports they had demanded 50m naira (around $384,000).

Oil workers are often kidnapped in the Niger Delta but are almost always released unharmed after ransoms are paid. The payments are always officially denied.

Her kidnapping follows the seizure of several children in the area in recent months.

The militants say they are fighting for more local control of oil wealth but some kidnappings are undertaken by criminal gangs.