Workers Party President and former lawmaker Rashed Khan Menon was arrested in Dhaka on Thursday.
Md Obaidur Rahman, Additional Deputy commissioner of Media and Public Relations Division of Dhaka Metropolitan Police, said detectives detained Menon, also a leader in the Awami League-led 14-party alliance, from Gulshan area of the capital at around 5PM on Thursday.
He will be produced before the court on Friday.
Earlier, on Thursday morning, a case was filed with Dhaka Metropolitan Magistrate Saiful Islam's court against Menon for making defamatory remarks about the Zia family.
The court directed the Police Bureau of Investigation (PBI) to investigate the case and submit a report.
Meanwhile, Menon has been implicated in a case filed with the International Criminal Court on August 19 (Monday) over the killing of a college student Alvi in Mirpur of the capital during the recent Anti-Discrimination Movement.
He is also accused in a case filed with the Tribunal over the mass killing during the Hefazat-e-Islam rally in Shapla Chattar (Roundabout) in Motijheel of Dhaka on May 5, 2013.
However, the police have not yet confirmed the specific charges or the case under which Rashed Khan Menon has been detained.