Shell has evacuated personnel from its Nigerian oilfields due to a mounting militant threat in the country’s Niger Delta region.

Shell’s decision came a few days after a group calling themselves the Niger Delta Avengers attacked Chevron’s offshore Okan oil platform in south-eastern Nigeria’s Delta State.

Because of this attack, around 90,000 barrels a day of output were stopped.

In February, the same group attacked a Shell oil pipeline, prompting the closure of the 250,000 barrel-a-day Forcados export terminal.

"We have very unique problems in terms of pipeline security."

The Wall Street Journal cited source familiar with the matter as saying that nonessential staff levels had been reduced at Shell’s Eja oilfield, located 15km off the coast of Nigeria.

Shell Nigerian subsidiary spokesperson said that the company is monitoring the security situation in Niger Delta, where it operates and is taking steps to ensure the safety of staff and contractors. The company evacuated 98 personnel from its Eja Oml 79 oil production facility, which is run by its Nigerian subsidiary, Shell Petroleum Development Corporation (SPDC).

Shell also evacuated some of its workers working at the Bonga field, located near the Eja oilfield.

Bloomberg quoted Nigeria Minister of State for Petroleum Emmanuel Kachikwu saying: "We have very unique problems in terms of pipeline security.

"We are aware that in the last few days, pipelines have been blown, but this should not make us lose hope."