Six foreign oil workers were kidnapped and a Nigerian sailor was killed when dynamite-wielding militants attacked an oil vessel early Tuesday, a navy spokesman said.
The region's main militant group, the Movement for the Emancipation of the Niger Delta, claimed responsibility in an e-mail.
Capt. Obiora Medani said the sailor was a guard aboard the Chevron Corp. ship, which was attacked off Bayelsa state, in the oil-rich south of the West African country. Medani said the vessel, named FPSO Oloibiri, is stationed offshore to store crude oil.
A Nigerian spokesman for California-based Chevron said the company had shut down an oil station that supplies the ship because of the attack, decreasing production by 15,000 barrels a day.
Chevron's Tope Idowu said four Italians, one American and one Croatian were abducted. Idowu said the American worked for Chevron in Nigeria while the rest were employees of a subsidiary, Chevron Shipping Co.
No demands have been made on the company by the attackers, he added.
The claim of responsibility came from an e-mail address used by MEND and said the attack was to demonstrate the group's continued strength to both the departing Nigerian government and the incoming administration following recent elections.
"We will continue with our struggle for justice until we achieve all our goals without exception," the group said.
The group promised to released the hostages on May 30 as long as their was no attempt to free them _ such as offering a ransom. MEND has repeatedly demanded the release of two imprisoned leaders charged with treason and corruption and greater control over the region's oil wealth.
Oil prices edged higher Tuesday after word of the kidnapping surfaced. Light, sweet crude for June delivery rose 1 cent to US$65.72 a barrel in electronic trading on the New York Mercantile Exchange at midday in Europe. Brent crude for June on London's ICE Futures exchange was up 23 cents to US$67.88 a barrel.
The latest violence in Nigeria "has once again highlighted the instability in the region, with the country's output still below full capacity and the most recent presidential elections have only made the situation worse," said Michael Davies, an analyst at Sucden in London.
In a separate incident Tuesday, gunmen seized the mother of the newly elected governor of neighboring Rivers state, police said.
Police Commissioner Felix Ogbaudu said the mother of Governor-elect Celestine Omeiha was kidnapped overnight from her home. The kidnappers have not yet made any demands.
"We have some clues and we are working on it," Ogbaudu said.
Nigeria is both one of Africa's richest countries and one of its most problem-laden, with vast oil reserves but also rampant corruption and violent crime. Ballot-box stuffing was widespread in recent nationwide elections in which the governing party claimed victory, dismissing criticism by international and domestic observers.
Omeiha, a member of the governing People's Democratic Party, was elected governor of Nigeria's richest state in the poll two weeks ago. On the day of the vote, two police stations were set afire and seven officers killed.
The parents and sister of an opposition candidate for the legislature were kidnapped, and he was told his family would be murdered if he discussed election irregularities.
The following week an attempt was made to kidnap the candidate who would become vice president-elect as he returned to vote in his home in the oil delta.
Competition is fierce for lucrative government posts in Africa's largest oil exporter. Despite generating tens of billions of dollars in oil revenue annually, most people live below the poverty line and massive government corruption has meant social services are largely nonexistent.
Rivers state alone has an annual budget of US$1.3 billion but most of the money designated for roads, clinics or schools has been stolen.
Kidnapping foreign workers for cash has become common in the lawless region. However, the rate of attacks has fallen during last month's elections as armed groups hired themselves out as political thugs.
Associated Press Writers Dulue Mbachu in Lagos and Dan Udoh in Port Harcourt contributed to this report.