A leader of a Niger Delta oil militant group unseen in public since his arrest has failed to appear before a Nigerian court as expected.

At a court hearing in the capital, Abuja, it was revealed that Henry Okah was charged in absentia last year with treason and other offences.

Lawyers for Mr Okah are meeting the Attorney General to arrange to see him.

Mr Okah’s lawyers say they believe he and another man arrested at the same time are still alive.

The Movement for the Emancipation of the Niger Delta (Mend) issued a news release last week threatening “anarchy” if Henry Okah is not shown in public.

Prosecutor Salihu Aliyu said the government was following the rules in its conduct over Mr Okah.

“It is up to the court to order a defendant be produced,” he said after the hearing.

The defence was handed a copy of the 14 charges made against Mr Okah in December, after his arrest in Angola, but before he was extradited to Nigeria.

The 14-count charge includes treason. If found guilty, Mr Okah faces the death penalty.

Another court hearing has been set in April for Mr Okah to be arraigned.

Mr Okah was extradited to Nigeria from Angola on gun running charges last month.

The government has said he is “safe and well” but has so far refused to allow any access to him.

Arrest

Mr Okah and Edward Atatah, a captain in the Nigerian Merchant Navy, were arrested in September in Luanda.

Interpol says they were buying arms and explosives, but they claim they were buying a second hand trawler for a marine engineering business.

Police say Mr Okah is being charged with murder, bank robbery, kidnapping, endangering the state and gun-running.

Mend came to prominence in 2006 after the arrest of another militant leader, Mujahid Dokubo Asari.

They kidnapped foreign oil workers for ransom, holding them deep in the creeks of the swampy Niger Delta and sending their pictures to international news desks, along with demands for a bigger share of the oil wealth.

Oil companies have slashed production and evacuated many staff to safer areas.

Since then copy-cat groups have started attacking softer targets like Nigerian national staff, the relatives of politicians and children.

A German worker was briefly held before being released this week - the first kidnapping of a foreign worker this year.