The Anglo-Dutch oil giant, Shell, has withdrawn staff from oil facilities in Nigeria's troubled Niger Delta.
By Anna Borzello
BBC correspondent in Ilorin, western Nigeria
The evacuation of 254 non-essential staff follows a new wave of increased violence in the region.
It comes as the military and police increased their operations against armed groups who operate in the swamps and creeks of the Delta.
Nigeria is the sixth largest producer of oil within Opec, but close to 70% of the population live in poverty.
The Shell workers were moved out from two oil facilities in the Soku and Ekulama areas of River State as a result of what they describe as the tense security situation in the region.
Shell produces about half of Nigeria's crude oil, but the company said there had been no disruption to production.
Earlier this month, the Nigerian military launched an operation to flush out armed militants living in the swamps and creeks near the oil city of Port Harcourt, following a day-long attack on the city itself which left five people dead.
The human rights organisation, Amnesty International, has since said that 500 civilians may have been killed and thousands of others displaced in the ongoing security crackdown.
The militants, known as the Niger Delta People's Volunteer Force, say they are struggling for the independence of the region's Ijaw people.
But the authorities instead allege they are involved in the lucrative trade of stealing and smuggling crude oil, which each year loses the country about 10% of its total oil revenue.