Gunmen in speedboats kidnapped six workers from an oil vessel, off Nigeria’s coast at dawn on Saturday, the second attack on an oilfield in a week, officials said.

The Polish, Filipino and Nigerian workers were seized from the Mystras, some 85 km (50 miles) offshore, Italian energy giant Eni SpA said on its web site. Another Nigerian worker was reported to have been wounded in the leg, the statement said.

The Mystras, used for production, storage and offloading crude oil, is capable of producing 80,000 barrels of oil per day. An Eni spokesperson refused further comment.

Militants have kidnapped more than 150 foreigners this year to press their demands for local control of oil revenues. The attacks since late 2005 have cut Nigeria’s regular output by about 20 percent, helping send crude prices toward all-time highs.

Locals have for years demanded a greater share of the wealth in Africa’s largest crude producer, and the region remains desperately poor despite its great natural bounty. The government of President Umaru Yar’Adua has stepped up efforts to maintain calm in the Niger Delta, and violence has waned since he took power on May 29.