Hundreds of angry Nigeria villagers chased workers away from an oil-transfer facility in hopes of forcing payment from the oil industry.
Elsewhere in the Niger Delta, gunmen were holding some two dozen Nigerian workers and security forces hostage at another flowstation that had been overrun on Sunday.
Authorities hadn't been able to access the interior of that facility and had no information on any casualties among the hostages, said Brig. Gen. Lawrence Ngubane, a military commander in the Niger Delta.
He said the invaders were threatening to blow up the station if security forces came near. Gunmen and troops battled in the area last week, leaving several gunmen dead.
ENI SpA, whose subsidiary Agip runs the facility, confirmed that the installation had been overrun, but gave no information on whether oil had stopped running through it. Agip officials in Nigeria had no immediate comment.
In the protest occupation that flared Monday, rough estimates showed nearly 1,000 people at the flowstation outside the main city of Warri, said Ngubane.
The villagers want money they say they're owed by U.S.-based Chevron Corp., which runs the facility, for restitution after an oil spill in their area, he said. Chevron officials weren't immediately available for comment.
Hundreds of flowstations dot the Niger Delta where Nigerian crude is pumped. The stations connect the tubes leading from wells into larger pipeline arteries that carry the crude oil to export terminals.
Protest occupations of oil facilities are common in the region, which remains deeply poor despite the vast natural bounty.
Nearly two years of spiraling violence in the oil-producing southern Niger Delta have cut Nigeria's crude output by about one quarter, sending oil prices higher in overseas markets.
New President Umaru Yar'Adua has said the crisis is one of the most-pressing matters he faces and a top militant leader was released on bail last week, marking a breakthrough in the conflict pitting militants against security forces.
The militants are pressing for more government-controlled oil-industry funds for their region, which remains desperately poor despite its vast natural bounty.
But their stepped-up attacks have helped degrade overall security conditions in the vast region of creeks and swamps and criminal gangs who kidnap foreigners now operate with apparent impunity. Some 200 foreign workers in the region have been kidnapped since December 2005, including more than 100 this year alone.
In addition, tension over local grievances such as a community accusing an oil company of failing to make good on promises of financial help sometimes results in attacks or kidnappings.
Nigeria is Africa's biggest oil producer and one of the top overseas suppliers to the United States.
In the capital Monday, labor unions called for a general nationwide strike to protest a government price hike on automobile fuel. The strike is to begin Wednesday and the unions said it would continue until the increase is repealed.
Ex-President Olusegun Obasanjo ordered the 15 percent fuel-price hike in the last days of his administration, which ended May 29 with President Umaru Yar'Adua's inauguration.
The unions are also protesting his hike on the value added tax, which sent costs on everyday items higher, and sale of two refineries where union workers are employed.
Automobile fuel in Nigeria is deeply subsidized by the federal government, which says it wants to end the practice to free up cash.
Impoverished Nigerians see cheap fuel as one of the few benefits they derive from the state. A liter of fuel in Nigeria costs around 60 U.S. cents.
The unions called for solidarity from all Nigerians, saying vehicles should stay off roads during the strike. Many Nigerians, however, live subsistence existences and need to work each day to buy food. Previous strike calls have gone largely ignored.