Three Filipinos were abducted by unidentified gunmen on Friday on their way to work at a natural gas export plant in southern Nigeria, police said.
The abduction of the contractors working at the Nigeria Liquefied Natural Gas complex in Bonny follows the abduction of a German from the nearby city of Port Harcourt on Thursday, and comes amid an increasingly bloody insurgency by militants fighting for local control over the Niger Delta's oil wealth.
"A group of gunmen intercepted their car, shot their tyre, fired into the air and took three Filipinos away in a speedboat," a police spokeswoman said.
Militants from the Movement for the Emancipation of the Niger Delta (MEND) have waged a campaign of kidnapping and sabotage against the world's eighth largest oil exporter, which has cut crude output by a quarter since February.
A MEND spokesman told the agency they were not involved in the abduction of the German.
"He was taken by a criminal band for ransom," the spokesman said in an email.
Well armed criminal groups, some involved in large-scale theft of crude oil from pipelines, regularly attack oil and gas installations and workers to extort money or get other concessions from companies.
Hostages are usually released unharmed after a few days after the payment of a ransom, which analysts say fuels the cycle of violence.
The Niger Delta is a vast wetlands region almost the size of England which is home to all Nigeria's oil and gas.
Most of its people live in poverty and much of the money meant for local development is stolen by elected officials.
The Nigeria Liquefied Natural Gas complex in Bonny is one of the world's largest such plants, exporting 18 million tonnes of frozen, pressurised gas in tankers to power stations in Europe and the United States.
Company officials were not immediately available for comment.