The Committee to Protect Journalists, along with 18 other organisations, has written to Nigeria President Muhammadu Buhari, appealing for the release of journalist Jones Abiri.
According to a statement by the CPJ, Abiri has been held by Nigeria's Department of State Security (DSS) for nearly two years.
It further called for the DSS to be held accountable for its attacks against journalists in Nigeria.
"We were disappointed that, after repeated requests during CPJ's visit to Nigeria in April 2018, we were not permitted to visit Abiri in detention," the CPJ said.
"In a meeting with CPJ on April 24, 2018, Garba Shehu, your presidential spokesperson, confirmed that Abiri remained in DSS custody and said he would be charged in court on allegations of being a militant. Yet after almost two years behind bars, Abiri has not seen a courtroom, nor has his family been given any information about his health and well-being."
The CPJ said the DSS operates under Nigeria's coordinator of national security, which reports directly to Buhari, according to the 1986 National Security Agencies Act.
"During a visit to State House in April, Garba Shehu also told CPJ that you would be made personally aware of Abiri's ongoing detention. We therefore call for your swift action to ensure Abiri's release and that those responsible for his prolonged and illegal detention are held accountable."
In February and March 2018, the DSS also arrested Tony Ezimakor, the Abuja bureau chief of the privately-owned Daily Independent newspaper.
CPJ documented Ezimakor's week-long detention without charge or court appearance, during which the DSS threatened the journalist with terrorism charges for his reporting.
Over the last two years, CPJ has repeatedly tried to contact Lawal Musa Daura, director general of the DSS, and Gbeteng Bassi, director of operations of the DSS, without success.
Nigerian journalists have similarly told CPJ, with dismay, that they are unable to reach the DSS for comment, regarding the arrest of their colleagues or otherwise, CPJ said.
During the same April 2018 meeting with CPJ, Garba Shehu confirmed that the DSS has not designated anyone responsible for communicating with the Nigerian public.
"We urge you to improve accountability and make the DSS accessible to the press. This includes the appointment of a DSS spokesperson," CPJ said.
"Your action to ensure the safety of journalists and the promotion of open dialogue through the press is made even more important because Nigeria will hold elections in February 2019. Around the world, CPJ has documented how attacks on journalists have escalated during election periods and other political processes.
"It is in this context that we urge you to take decisive action to ensure that journalists are free to report on matters of public concern, and that a culture of self-censorship does not cloud public decision-making processes. As part of this, Abiri should be released without delay."
Among the organisations supporting the appeal alongside CPJ, are the Nigerian Union of Journalists, the Robert F. Kennedy Human Rights centre, Human Rights Concern in Eritrea, CIVICUS, the Community Empowerment for Progress Organization of South Sudan, the Association For Human Rights In Ethiopia (AHRE), the West African Human Rights Defenders Network (ROADDH/WAHRDN), the Nigeria Network of NGOs and Amnesty International Nigeria.
- African News Agency (ANA)