The Indigenous People of Biafra says intelligence agents arrested a leader calling for the peaceful secession of the southeast from Nigeria — a cause that prompted a civil war in the 1970s in which an estimated million people died.

That group and the Movement for the Actualization of the Sovereign State of Biafra say Radio Biafra director Nnamdi Kanu was detained Saturday as he tried to fly to London from the airport of the commercial center, Lagos.

It was not immediately possible to get comment from the Department of State Security.

In July President Muhammadu Buhari's government said it had jammed Radio Biafra's airwaves because it is unlicensed but the station is still able to broadcast, airing grievances of the Igbo tribe who accuse the government of discrimination.