Police and oil company officials in Nigeria say gunmen are holding about 60 people hostage at a security base attached to a Shell Oil facility in southern Bayelsa state.
Gunmen overran the facility early Tuesday and took the hostages. Authorities have not identified the militants or the hostages.
There are no reports of deaths or injuries. Government negotiators are on the scene.
Such attacks on oil-producing operations are common in Nigeria's Niger River Delta.
Nigeria is Africa's largest oil producer and normally pumps more than 2.5 million barrels per day. However, militant attacks have cut the country's production by at least 25 percent.
The militants are demanding that impoverished communities in the Niger Delta get a greater share of the region's oil revenue.
Some information for this report was provided by AFP and AP.