Assailants in three boats seized the four oil workers from a support vessel attached to Shell's EA oil platform off the southern oil-rich Niger Delta on Wednesday afternoon, Shell spokesman Andy Corrigan said by telephone from London.
Corrigan said it was unclear if the hostages were working for Shell or one of its contractors. He declined to give further details, including the nationalities of those abducted, "for safety and security reasons."
Graeme Bannatyne, spokesman for the British Embassy in Nigeria, said it believed one of its nationals was among the hostages.
Local communities in Nigeria have been demanding a greater share of revenues from the oil flowing from their land for years. Hostage-taking is common, and kidnapped workers are usually released unharmed.
Shell workers running the EA platform have been taken hostage twice in the past year over disputes with neighboring communities, who accuse the company of reneging on a promise to undertake development projects for their impoverished region.
A Croatian was seized in December 2004 and freed days later. Two Germans and four Nigerian oil workers were similarly taken hostage in June and later freed.
Nigeria produces about 2.5 million barrels of oil a day.