The Pakistan Press Foundation (PPF) has written to President Muhammadu Buhari over the continued detention of Premium Times journalist Samuel Ogundipe.
In the letter dated August 16, the PFF, an independent non-governmental institution committed to promoting and defending freedom of expression, expressed concern over the detention of Mr Ogundipe who has now been in police custody for about two days.
"PPF condemns this action and urges the Nigerian government to immediately release Samuel Ogundipe and investigate the matter and bring those responsible to justice. PPF also urges you to take decisive action to promote and respect freedom of expression and the press," the organization wrote in the letter signed by Owais Aslam Ali, its Secretary General.
Like the PFF, Action Aid, a non-governmental organisation, has condemned Mr Ogundipe's arrest, describing it as an attempt to undermine press freedom and the principles of democracy.
Nihinlola Ayanda, Communications Coordinator, Action Aid, made this assertion in a statement in Abuja on Thursday.
Ms Ayanda quoted the organisation's Country Director, Ene Obi, as saying that the arrest of the journalist without legal representation and access to his lawyer should be totally condemned.
According to Mrs Obi, Mr Ogundipe's arrest, torture, bank account freeze, secret arraignment without legal representation by the Nigerian Police is condemnable as such acts undermine press freedom and Nigeria's hard-earned democracy.
"Nigeria is not a police state, so journalists should not be persecuted for executing their responsibility of informing and educating the public.
"The Freedom of Information Act (FOIA) allows citizens access to public records and information held by public officials or institutions.
"It empowers newsmen to discharge their duty fairly and truthfully and the government has the responsibility of upholding the law and promoting democracy without any form of press bullying," she said.
She noted that if any media organisation had published any information that was not true, relevant authorities should seek civil ways of dealing with such issues.
Mrs Obi called on the Nigerian police and other security agents to refrain from arresting journalists, who were fulfilling their constitutional obligations as enshrined in Section 22 of Nigeria's Constitution.
She said if this was followed, it would make it obligatory for the media to hold public office holders accountable.
She, however, described Mr Ogundipe as "courageous" while calling on journalists not to desist from carrying out their constitutional obligations in promoting the country.
In its reaction, the Advocacy for Integrity and Economic Development (AIED) called on Acting President Yemi Osinbajo to terminate the appointment of the Inspector General of Police, Ibrahim Idris.
The organization in a statement on Thursday by its Director of Media and Publicity, O'Seun John, described the continuous incarceration of the reporter as an assassination of the values of democracy and a stampede on Press Freedom.
"We were shocked to receive news of the unlawful detention of Samuel Ogundipe, one of the finest investigative reporter in Nigeria who has only dedicated his time to revealing the truth at all times.
"We find it incomprehensible that this illegality took place at a time the Acting President, Professor Yemi Osinbajo - a senior minister in the temple of justice - is making efforts (to) reform the scattered structure of the Nigeria Police Force.
"This act in itself is nothing other than treason as it undermines the office of the Acting President and brings ridicule to the Presidency.
"We believe strongly in the face of glaring evidences of gross abuse against human rights and total disregard for the tenets of law that the Inspector General of Police has outlived his usefulness in office and his appointment should be terminated without delay," the group said.
Mr Ogundipe was arrested on Tuesday and secretly tried without legal representation on Wednesday.
His arrest has been condemned by local and international rights groups.