Separatist militia leader Moujahid Dokubo-Asari looks on as he appears before a court in the capital of Abuja

Armed militants in Nigeria have issued what they call a "final warning" of major attacks on oil companies in the nation's oil-rich Niger Delta region if the government does not release their leader.

A statement by the militants Friday, gives the government until Saturday to release their leader, Moujahid Dokubo-Asari. Otherwise, the militants say they will carry out their threat to destroy all oil production in the Niger Delta. They advise oil firms to evacuate their staff before the deadline.

About a hundred ethnic Ijaw militants from the Niger Delta People's Volunteer Force seized an oil plant Thursday operated by the U.S oil company Chevron, forcing it to shut down operations.

Police arrested Mr. Dokubo-Asari on Tuesday and charged him with treason for comments he made supporting the breakup of Nigeria.