Plainclothes policemen detained Jatiyatabadi Swechchhasebak Dal president Shafiul Bari Babu from Jatiya Press Club area on Tuesday.
A team of Detective Branch of police picked him up while he was returning home from the press club area after joining BNP's human chain programme around 11:45am.
Contacted by UNB, BNP senior joint secretary general Ruhul Kabir Rizvi confirmed Babu's detention.
He strongly condemned and protested the detainment of Swechchhasebak Dal president and demanded his release immediately.
Earlier, as part of countrywide scheduled programmes, BNP leaders and activists formed a human chain in front of the Jatiya Press Club demanding their chairperson Khaleda Zia's release from jail.