As of now, Chevron's operations in the Niger Delta are completely offline following attacks on its facilities, a militant group proclaimed.

A group calling itself the Niger Delta Avengers said it launched attacks on pipelines and wells operated by the Nigerian National Petroleum Corp. and Chevron. The group said the attacks came after issuing an ultimatum to the Nigerian government about developments in the Niger Delta.

"As at now, Chevron's operation in the Niger Delta is zero," spokesman Mudoch Agbinibo said in a statement.

Another group, the Movement for the Emancipation of the Niger Delta, launched a string of attacks against energy infrastructure in the area in 2013. The militant group said its campaign was a response to rampant oil theft in the region. It said Nigerian security forces "aided and abetted" the theft.

In its statement, Agbinibo said his movement was akin to the biblical prophet Moses. "All we are asking is to let our people go," he said.

All international oil companies and the federal government of Nigeria are criminals, he added.

In March, Nigerian Petroleum Minister and Managing Director of the Nigerian National Petroleum Corp. Emmanuel Kachikwu said the state oil company would be split up into dozens of distinct entities in an effort to address corruption and revenue losses.

Nigeria's oil-dependent economy has struggled under the strains that have emerged since crude oil prices first dropped below the $100 per barrel mark in 2014. The International Monetary Fund warned the impact of lower oil prices were adding to pressure from an economy in need of deep structural reforms. From the pressure of oil prices alone, the government's deficit doubled to about 3 percent of the gross domestic product last year.

A spokesman for Chevron was quoted as saying in The Punch, a Nigerian newspaper, that the company was still assessing the amount of damage, but confirmed Chevron had shut down its facilities in the Niger Delta.

"All of our export commitments are taken care of," he said. "It will not affect our commitments to export crude."