Nigeria's government freed a prominent rebel leader from jail July 13, his lawyer said, meeting a demand by insurgents who have been attacking the country's oil installations and kidnapping oil workers.

But it was unclear what had motivated the government to make the concession since the Movement for the Emancipation of Niger Delta, or MEND, rebels have said that Henry Okah's release would not lead them to end their attacks in Africa's top oil-producing nation.