The U.S.-based Committee to Protect Journalists has called on Nigerian authorities to "investigate and hold accountable the police officers" who allegedly beat and threatened journalist Kofi Bartels.
CPJ said Bartels told the committee that on Tuesday he was beaten and arrested for trying to film several officers who he said were beating a young boy.
Bartels, a journalist with Nigeria Info, also tweeted about the attack in the city of Port Harcourt.
Bartels told CPJ that an officer told Bartels that he had "been giving them problems for a long time," citing his work covering the police in Rivers state. He said the officer also threatened to put him in a prison cell with an inmate who would rape him.
Bartels was not charged with any crimes and eventually released.
"The police officers involved in this horrific alleged assault against Kofi Bartels must be swiftly brought to justice," said Angela Quintal, CPJ's Africa program coordinator. "The initial assault of a reporter documenting police behavior, compounded by the brazen retaliation for past reporting, is a chilling example of a gravely consistent pattern of Nigerian security services' violence against journalists."
Also Thursday, Nigeria's broadcasting authority shut down a private radio and television station owned by a key opposition figure.
The National Broadcasting Commission (NBC) said it had suspended the license of Daar Communications, the owners of African Independent Television (AIT) and RayPower FM radio.
Officials said both media entities had failed to follow the Nigerian broadcasting code, but did not elaborate.
The owner of two broadcast stations, Raymond Dokpesi, who is also a key member of opposition Peoples Democratic Party, had predicted the move by the NBC. Hours before the licenses were suspended, Dokpesi told reporters at a news conference that his staff was being intimidated on the instruction of the Nigerian presidency.
"We are on a road previously traveled. A media and press clampdown is in the offing," he told reporters.