Kidnappers in Nigeria freed eight foreign oil workers Sunday, two days after they were seized in an unprecedented raid on a rig far offshore.

The kidnapping heightened fears in an oil industry hurt by a series of militant attacks.

Gunmen had captured six Britons, one American and one Canadian from a rig 64 kilometers out to sea on Friday. Two Britons were freed early Sunday and the other men several hours later, local authorities and the British embassy said.

"They are all safe and well. We have handed them over officially to the representatives from Peak," said Johnny Iganiwari, information commissioner for Bayelsa state where the men were held captive. Peak Petroleum is a Nigerian company that operates the Bulford Dolphin rig where the hostages were seized.

Iganiwari and a source from one of Peak's partner companies said the released men were in the Bayelsa state capital Yenagoa and talks were under way to decide where they would go next.

The abductions on Friday followed a series of militant attacks earlier this year that have shut down a quarter of oil output from OPEC member Nigeria, Africa's top producer.

Authorities declined to comment on whether a ransom had been paid, but a security source close to the situation said money had changed hands.

Kidnappings for ransoms are common in the Niger Delta, a vast, impoverished wetland that produces the bulk of Nigeria's 2.4 million barrels per day (bpd) of crude oil. Local people have seen few benefits from the industry.

Oil companies deny paying money to secure the release of kidnapped staff, but security analysts say they usually do pay up and this encourages abductions.

The militant Movement for the Emancipation of the Niger Delta (MEND), whose attacks have forced the closure of about 550,000 barrels per day of oil production since February, said on Saturday it was not involved in the latest abductions.

The kidnappers had not listed specific demands but wanted to force the oil companies to negotiate on a range of issues including employment for local people, environmental impact and development projects, sources from the companies involved said.

Attacks on facilities onshore or in shallow water are frequent in the Niger Delta, but security sources said they were unaware of any previous raid as far away from the shore as the Bulford Dolphin rig.

The sophisticated night-time attack by 20 to 30 gunmen in speedboats showed that even deep offshore facilities are no longer safe in the world's eighth-biggest exporter of crude.

The rig is owned by the Norwegian oilfield services group Fred Olsen Energy ASA and leased to Peak, which operates it in partnership with Equator Exploration.

The attack had no impact on oil output as the facility is an exploration rig that will not produce crude for years.

(China Daily June 5, 2006)