LAGOS (AFP) - Heavyily armed rebels seized a Briton, a Croat, a Russian and four Nigerians from an oil rig run after a three-hour gunbattle Sunday off southern Nigeria, industry and security sources said.

The heavily armed rebels attacked the platform, owned by the Anglo-Dutch giant Shell, on speed boats and made off with the hostages, the sources said. But no casualties were reported from the battle.

A Shell spokesman told AFP the shooting lasted "about three hours" at the production, storage and offloading facility, which had been operational for five years.

The facility was evacuated after the attack, he said.

The British Foreign Office confirmed that a British citizen had been abducted.

More than 200 foreigners, mostly oil workers, were kidnapped in the Niger Delta in the 18 months to June amid a rebellion over distribution of oil revenues in the energy-rich region.

Draconian security measures put in place by companies have reduced the abductions in recent months but markets remain jittery over any threats to production as crude prices hit new highs.

The unrest has reduced exports of Nigeria's 2.6 million barrels of crude per day at peak production by a quarter. Nigeria is Africa's biggest oil producer but the country remains desperately poor.

Shell is the biggest operator in the Niger Delta, accounting for half the volatile region's daily production, and has been a regular target for the rebels.

Kidnappers demanding a high share of the oil wealth have changed tactics in recent weeks in response to the tougher security, targeting the families of oil workers, lawmakers and prominent Nigerians.

The five-year-old son of a Nigerian Shell worker was kidnapped five days ago and last month the two-year-old daughter of a Shell employee was snatched before being released a week later.

Most abductees have been released unhurt after days or even weeks, usually after ransoms are paid, although oil firms rarely admit to making such payments.

Earlier this month a British oil worker, David Ward, was freed after spending two months in rebel captivity in the Niger Delta.

Italian oil company Saipem is understood to be negotiating with the kidnappers of a Colombian employee who was seized in Nigeria last month in an attack in which another Colombian worker was killed.

Copyright 2007 Agence France Presse.