Omoyele Sowore, convener of Revolution Now Movement, has been released after an initial arrest.
Sowore was arrested at the Federal High Court in Abuja on Monday morning.
The publisher of SaharaReporters had stormed the court over the trial of Nnamdi Kanu, leader of the Indigenous People of Biafra (IPOB).
“I have just been arrested by the Nigerian Police at the Federal High Court. Subjected to beatings by police officers and taken to the Federal Secretariat police station,” SaharaReporters quoted him to have said.
But Sowore, who was released after about an hour, addressed newsmen.