The Niger Delta Avengers group posted a map on social media suggesting that the West African power house could divide into five countries.
Analysts had predicted that the stunning result of the British referendum to leave the EU would encourage separatists in Nigeria. "Separatist groups will feel emboldened," Nigeria's SBM Intelligence warned in an analysis of the fallout from the British vote.
"President (Muhammadu) Buhari should call for a referendum to enable every Nigerian to vote if they want to stay as Nigerians or not, just like what David Cameron of Great Britain did," the Avengers posted on Twitter.
Based in the southern Niger Delta, the Avengers have allied themselves with separatist groups from the southeastern Igbo people, and said they, too, might demand a separate state. Igbo separatist groups have had a resurgence in the past year. Nigeria suffered a civil war from 1965 to 1970 that killed a million people after the Igbo declared an independent state of Biafra. Former colonial power Britain sided with the federal government while France supported the secessionists.
All Nigeria's oil production is in the Niger Delta and offshore of the southern region. Oil militants and non-violent activists have been demanding a greater share of the wealth from oil, an industry that has massively polluted their lands and destroyed the livelihoods of communities that rely on fishing and agriculture.
Oil provides 70 percent of the federal government's revenue. Finance Minister Kemi Adeosun said the Avenger's attacks — on facilities of U.S.-based Chevron, Dutch-British Shell and Italian Agip — cost the government nearly $60 million in May. The attacks have stopped production at two of Nigeria's five oil refineries, disrupted supplies from two export terminals and made buyers cautious of Nigerian oil.
Nigeria also confronts an Islamic extremist uprising in the northeast by a group allied with the Islamic State that has killed more than 20,000 people and an upsurge in deadly confrontations in the Middle Belt between Muslim nomadic cattle herders and Christian farmers.