Residents say hundreds of heavily armed security men have taken up positions in the city, and movements around the courthouse are restricted.

Federal Director of Public Prosecution Salihu Aliyu was reluctant to comment on the trial.

"Well, I do not know. Let us put it that way. I am not in a position to comment," said Aliyu.

On Monday, a Nigerian court granted the request of federal prosecutors for a secret trial for Okah, citing national security considerations.

But Lagos-based lawyer, Festus Keyamo, criticizes the decision to conduct the trial in secret, saying it infringes on the rights of the accused.

"I think it is wrong to try him in private. It is wrong to arraign him in private, for such a matter that is very, very important. It has international concerns and dimensions, and even in respect of protecting his human rights," said Keyamo. "He has the right to be heard publicly, he has the right to open trial, he has the right to defend himself in public. I condemn any move to try him in secret."

Okah's group, the Movement for the Emancipation of the Niger Delta, carried out a series of pipeline bombings and kidnappings of foreign oil workers in 2006, forcing the closure of about 20 percent of Nigeria's oil output.

The group has pulled out of planned Niger Delta peace talks to protest Okah's arrest and trial.

Impoverished local communities in the Niger Delta are demanding greater control over the region's oil wealth. They claim five years of oil extraction have damaged the environment and enriched foreign oil companies and corrupt Nigerian officials. source: voa