LAGOS (Reuters) - A rebel faction from Nigeria's oil-producing Niger Delta said on Friday its leader, Henry Okah, had been "illegally" extradited from Angola where he was arrested on gun-running charges last September.
There was no immediate comment from Nigerian authorities. Nigeria had previously said it wanted Okah extradited but that would be difficult as the two countries did not have an extradition treaty.
Okah's arrest had sparked a wave of attacks on oil facilities and the armed forces in the Niger Delta, undermining the new government's efforts to negotiate a peace deal with several militant groups in the anarchic delta. His extradition is likely to increase tensions in the delta.
Angola's state-run ANGOP news agency said Okah and another Nigerian facing similar charges were both extradited on Thursday and a ceremony was witnessed by Nigerian diplomats.
"Two Nigerian nationals who had been arrested by Angola's national police over alleged trafficking of arms and explosives in the country to carry out terrorist activities in the world were extradited Thursday from Luanda," ANGOP reported.
ANGOP did not say where Okah was taken to. His militant faction said he was being detained in northern Nigeria, though it did not say how it knew this.
"The Movement for the Emancipation of the Niger Delta (MEND) is following keenly the moves of the government to pin on Henry bogus and unfounded charges," the rebel group said in an email sent to journalists late on Friday.
"Such actions are unacceptable to the Supreme Command of MEND. For now, we appeal for calm to the peace loving people of the Niger Delta as we all watch to see the government's next line of action," the group said.
Okah, who has been described by other militant leaders from the Niger Delta as a powerful arms dealer, led a faction of the MEND whose attacks on oil production facilities in early 2006 shut down roughly a fifth of Nigerian output.
He said he was fighting to redress decades of injustice in the impoverished delta, where oil extraction has polluted the land and water and enriched corrupt politicians but brought few benefits to the people.
Many armed groups in the Niger Delta make similar claims, although the lines between militancy and crime are blurred. Such groups often profit from hostage taking and a lucrative trade in stolen crude oil.
The MEND has repeatedly splintered and alliances have shifted between rival leaders. A faction loyal to Okah, angry about his arrest in Angola, has shunned recent talks with the government and continued to blow up ships and pipelines.