Nigerian media reported Monday a group calling itself the Niger Delta Avengers forced the evacuation of facilities in the area operated by Royal Dutch Shell.

Nigerian newspaper Vanguard reported subsidiary Shell Petroleum Development Corp. evacuated around 100 staff from an oil facility that was producing around 90,000 barrels of oil per day. The newspaper reported that a skeleton crew was left behind, though operations at the Shell facility were suspended.

Vanguard reported the militant group calling itself the Niger Delta Avengers forced the Shell evacuation. The group last week took credit for knocking pipelines controlled by the Nigerian National Petroleum Corp. and Chevron offline. The group said the attacks came after issuing an ultimatum to the Nigerian government about developments in the Niger Delta.

The Nigerian newspaper quoted a source close to the militant group as saying it was determined in its operations against state interests.

"They will cripple oil and gas supply to the country as long as government remains recalcitrant to their demands," the source said.

There was no official statement from either the Niger Delta Avengers or Shell on the evacuations.

The Niger Delta Avengers in February launched a campaign it called Operation Red Economy. The purpose, it said, was to start a revolution aimed at wrestling the country away from the hands of the "wicked" administration of Nigerian President Muhammadu Buhari.

Advocacy group Global Witness in March said Shell and its partners in Nigeria may have exposed shareholders to a high level of risk in a corrupt system. The advocacy group said oil production license 245 was sold in the late 1990s for $20 million to a company "secretly owned" by then Nigerian Oil Minister Dan Etete and later sold to Shell and Italian energy company Eni for $1.1 billion.

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.