A court in Nigeria has charged the leader of a banned separatist group with treason.  His arrest last month sparked a wave of threats against oil installations in the volatile Niger Delta and an armed attack on a facility run by a U.S.-based petroleum company. 

The leader of the outlawed Niger Delta Peoples Volunteer Force, Mujahid Dokubo-Asari, shouted the word "freedom" to a group of supporters, as he was escorted into the courthouse in Nigeria's capital, Abuja.

Inside, Justice Babs Kwewumi read a list of charges against the separatist leader, including a treasonable felony and plotting to overthrow the government.  Mr. Asari pleaded not guilty, and was then quickly led back to jail under heavily armed escort.

He has been in custody in Abuja since his arrest at his office in the oil-rich Niger Delta's main city of Port Harcourt several weeks ago.

The charges against Mr. Asari stem from an interview he gave to a Nigerian newspaper, in which he is said to have called for the downfall of the country's federal state.

His arrest set off threats of violence by his followers against foreign oil interests in the delta region, which generates the majority of Nigeria's oil.

Armed supporters attacked an oil platform owned by American oil-giant Chevron, forcing it and another facility to shut down for several days.  Other oil companies in the delta were forced to limit travel by their employees.

Mr. Asari has long called for the secession of the Niger Delta region.  Last year, he threatened, what he called, a full-scale war on foreign oil interests. 

The situation, then, was calmed only after Mr. Asari met personally with President Olusegun Obasanjo.

A West Africa political analyst with the London-based research firm, Global Insight, Olly Owen, says it is not entirely apparent why Mr. Asari is being put on trial now.

"The timing of it is a little bit confusing," said Mr. Owen.  "It's not entirely clear what they hope to achieve by that.  One possibility is that, following his involvement with a pro-national conference organization that is agitating for more resource control over oil-producing areas, they began to view him as more of a credible political threat than he was previously."

Though Mr. Asari's supporters have, in the past, succeeded in disrupting oil production in the delta, they eventually backed down from threats to blow up oil platforms following his arrest last month.

Mr. Owen, who recently spent several weeks in the Niger Delta, says that does not mean they are not capable of spawning more violence in the area.

"I think, probably, their threat to affect things single handed is limited," he added.  "I think, the real problem that they can pose is in terms of the cue for action that they can give to other groups, so that other people who have grievances of their own, that they can map onto the Asari issue, will use it as a reason to take up arms or take direct action."

Despite its oil wealth, most people living in the Niger Delta remain largely impoverished.  Local groups have, for years, been demanding a larger share of oil revenues.  They also blame oil companies for widespread environmental damage.

If convicted of the charges against him, Mr. Asari could spend the rest of his life in prison.