Nigerian crude oil production will likely remain suppressed by militant activity at least through next year, a report from the U.S. government said.

The most active of the many militant groups in the oil-rich Niger Delta region, the Niger Delta Avengers surfaced early this year and have since contributed to a steep drop in crude oil production. Based on a report from the U.S. Energy Information Administration, total Nigerian crude oil production fell to a 30-year low this year.

"Crude oil production disruptions in Nigeria reached 750,000 barrels per day in May 2016, the highest level since at least January 2009," the EIA's report read.

The Niger Delta Avengers have been waging a militant campaign against national and international energy companies working in the Niger Delta. The group accused the government of Nigerian President Muhammadu Buhari of favoring oil and gas interests over the interests of the people in the Niger Delta.

In official statements, the group said it was countering the government's narrative that its campaign targeted Nigerian security forces and oil workers, instead blaming the administration of Buhari, a former military general, for some of the violence.

In an early August statement, spokesman Mudoch Agbinibo said the group was calling for the restructuring of the country, saying the Buhari administration was deaf to the plight of its citizens.

The EIA's report said the NDA's campaign has been "immediate" and "severe" for Nigerian oil production. The Buhari administration at one point this year suggested a truce was brokered with militant groups, but the Niger Delta Avengers said in an official statement that it had "not negotiated with anyone." The government, however, has continued with an amnesty program aimed to stemming the tide of violence.

"However, because payouts are just one of the NDA's many demands, crude oil production stoppages are likely to continue until the Nigerian government and the NDA can reach a comprehensive agreement," the U.S. government's report read. "EIA expects Nigerian oil production to remain depressed through 2017 as a result of militant attacks."