Many Twitter users in Nigeria are talking about #NnamdiKanu, the director of Radio Biafra, operated by people sympathetic to the campaign to create the breakaway state of Biafra.
A pro-Biafra group says Mr Kanu was arrested by Nigeria's secret police on Saturday, Vanguard newspaper reports.
In July, Nigerian authorities banned the station and jammed its signal.
Pro-secessionists in the south-east declared Biafra an independent state in 1967, but the military defeated them after a three-year civil war which claimed more than one million lives.
twitter: https://twitter.com/jokechukwuemek1/status/656071574743883776
