Congolese journalist Steve Wembi was targeted by "a raid (conducted) by agents presented as belonging to the National Intelligence Agency (ANR)," ACPI said in a statement.
He "has been detained in a hotel in central Kinshasa, but remains unaccounted for until now," the association added.
A reporter said on condition of anonymity that he saw Steve Wembi being taken away by these men in front of the hotel in a white jeep.
"He was never arrested by the services, in any case, I took my phone yesterday to check", said Tuesday evening on the official television (RTNC) the Congolese Minister of Communication and government spokesman, Patrick Muyaya, mentioning, on the other hand, a man "in hiding" without more details.
The New York Times expressed its concern.
"We are concerned about reports that Congolese journalist Steve Wembi has been arrested. Mr. Wembi is a well-known freelance journalist who has worked for media outlets including the New York Times, although he is not currently on assignment for the Times," said Nicole Taylor, a spokeswoman for the newspaper.
The ACPI added that another of its members, journalist Pascal Mulegwa, Kinshasa correspondent for Radio France Internationale (RFI), "who came to inquire about the situation of his colleague, was brutally arrested in front of the hotel and stripped of his personal belongings.
His belongings were returned to him "after more than two hours of detention in inhumane conditions in the premises of the ANR," the statement added. "However, a large sum of money was taken from him by agents of the ANR," continued the ACPI.
The Association "condemns these abusive acts against its members and demands that the competent authorities conduct appropriate investigations to locate" Steve Wembi. In its statement, it said it remains "concerned about threats and other pressure exerted on correspondents of the international press for months.
The situation is tense in the eastern DRC, which has been plagued by violence from armed groups for nearly 30 years and where the resurgence of the M23 rebellion has caused renewed tension with neighboring Rwanda. Kinshasa accuses Kigali of supporting the rebellion, which Kigali denies.
In his weekly briefing on Monday, Patrick Muyaya called on the press to "hold the media front" and "avoid playing into the hands of the enemy.
"We value the freedom of the press," he said Tuesday on RTNC.
"It is also important to know that we are in a state of war, that part of the territory is occupied and that information related to military news requires professional coverage," he insisted.
The DRC is ranked 125th (out of 180) in the latest world press freedom index established by the journalists' rights organization Reporters Without Borders (RSF).