Six Britons, one American and a Canadian were kidnapped from Bulford Dolphin on June 2 last year in a night raid by gunmen in speedboats. They were released two days later.


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


The Niger Delta, which accounts for all of Nigeria's approximately 2.5 million barrels per day (bpd) in crude exports, has been hit by a wave of abductions and attacks on oil facilities since late 2005.


Analysts say the violence in the delta is rooted in poverty and a collapse in basic public services due to endemic corruption in government.