LAGOS, Nigeria - Royal Dutch Shell shut down production from an offshore oil field that produces about 200,000 barrels per day after the most powerful militant group in Nigeria launched an attack on an installation there Thursday.
Oil prices rose in Asia on the news, which raised concerns about possible supply outages in Africa's largest oil producer.
A leader of the Movement for the Emancipation of the Niger Delta told The Associated Press that militants attacked the Bonga oil field more than 135 kilometres from shore.
But the militant leader, speaking on condition of anonymity, said his fighters weren't able to enter a computer control room, which they hoped to destroy.
"The location for today's attack was deliberately chosen to remove any notion that off-shore oil exploration is far from our reach,'' the group said in a subsequent statement.
"The oil companies and their collaborators do not have any place to hide in conducting their nefarious activities.''
Olav Ljosne, a spokesman for Royal Dutch Shell, confirmed an attack, but gave no details.
He said production had been stopped from the field, which normally produces about 200,000 barrels of crude a day.
That accounts for about 10 per cent of Nigeria's current daily output of about two million barrels, which is already significantly lower than the amount produced before years of militant attacks on crucial oil infrastructure.
The militants also said they kidnapped an American worker from a supply vessel they encountered while returning home from the attack.
The seizure was confirmed by private security officials, speaking on condition of anonymity because they are prohibited from speaking to the media. The officials said two other seamen on board were injured in that attack.
Over 200 foreign hostages have been seized since an upsurge of violence that began in early 2006. The hostages are normally released unharmed after a ransom is paid.
Attacks against offshore facilities are exceedingly rare. Oil industry officials consider their operations on the high seas much safer than those in the creeks and swamps of Nigeria's southern Niger Delta, where most of the attacks during two years of increased violence have taken place.
The turmoil in Nigeria's south has helped send oil prices to historical heights, giving the militants more leverage in their drive to force the federal government to ensure more oil industry proceeds remain in the region where the oil is produced.
Despite being the home of almost all of Nigeria's petroleum reserves, the country's south is as desperately poor as the rest of the country, which is Africa's most populous with 140 million people.
But criminality and militancy are closely linked, with many of the militant groups accused of stealing crude oil from wells and pipelines for sale in overseas market and helping politicians rig elections.
