Detective Branch (DB) of police detained BNP Joint Secretary General Syed Moazzem Hossain Alal from in front of the party's political office at Naya Paltan in the capital at 12.20pm on Saturday.
Police have charged baton on BNP leaders and activists who took part in its pre-scheduled ‘Black-Flag-Display’ programme.
BNP men took position with black flags in front of the office around 10am chanting slogans demanding the release of BNP chairperson Khaleda Zia.
Police used water cannons to foil the prograame.
Police arrested Alal while he was getting out of the office after the end of press-conference at the party office.