Detective Branch officers arrested former Gazipur-5 member of parliament Akhtaruzzaman, 73, from a residence in Gulshan at about 10pm on 5 August.
Dhaka Metropolitan Police said the arrest followed allegations that he was involved in the activities of a banned organization.
Police also said there were multiple cases against him, including a murder case.
Additional Deputy Commissioner Niaz Mehdi of the DMP Media and Public Relations Division said Akhtaruzzaman was being questioned.
Mehdi said further legal action would be taken.