A Nigerian court has charged the leader of a militant group with treason and plotting to remove President Olusegun Obasanjo from office.

Moujahid Dokubo-Asari pleaded innocent to the charges Thursday in an Abuja court, where he called out for freedom for his ethnic Ijaw people.

Police were deployed outside the court to prevent violence.

Mr. Asari was arrested last month after calling for the break-up of Nigeria in a newspaper article.

The arrest prompted his militant group, the Niger People's Volunteer Force, to threaten to destroy oil facilities in the oil-rich southern Niger Delta region unless he was released.

The militants briefly took over a flow station of the U.S.-based oil company Chevron, forcing the company to shut down two facilities. They later declared a cease-fire with the government.

Militants say they are fighting for a greater share of Nigeria's vast oil wealth.

Some information for this report provided by AFP and AP.