The incident comes a day after a German national was also seized in the nearby city of Port Harcourt.

Four armed men blocked the workers' vehicle as they were travelling to work at the Nigerian Liquefied Natural Gas plant, fired in the air and then took them hostage, one of their colleagues told AP news agency.

The men were working for Baker Hughes, a US construction company subcontracted to the Nigerian plant.

Kidnappings and attacks on oil facilities have become increasingly common in the country's southern delta as local militia groups fight for control of the region's rich oil resources.

Impoverished region

No group has yet claimed responsibility for the kidnapping and The Movement for the Emancipation of the Niger Delta, one of the largest groups operating in the region which has kidnapped several foreigners in the past, said it was not involved in either incidents.

 

Nigeria is Africa's largest oil producer and a major supplier to the United States. 

 

The Niger Delta is a vast wetlands region 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.

 

Locals also accuse many of the multi-national companies in the area of exploiting their resources and polluting their land.