Nigerian militants say they will blow up oil wells and pipelines later Wednesday, if the government does not release their leader, who they say was arrested.

The deputy leader of the Niger Delta People's Volunteer Force issued the ultimatum Tuesday and warned oil workers to leave the southern delta region.

Residents reported hearing gunfire overnight in the southern oil city of Port Harcourt, where militants reportedly took to the streets in protest.

The group says police arrested its leader, Mujahid Dokubo Asari, in Port Harcourt Tuesday and flew him to the capital, Abuja. Police would not confirm the arrest.

Militants in the Niger Delta say they are fighting for a greater share of the region's oil wealth. Last year, the militants threatened to wage an all-out war on Nigeria's government.

Some information for this report provided by AP and AFP.