Ratish Chandra Bhowmik, a respected prosecutor and champion of minority rights, has not been seen since he left his home in Rangpur early Friday morning.
His disappearance comes a fortnight after seven terrorists from the Jamayetul Mujahideen Bangladesh were sentenced to death for murdering the caretaker of a Sufi shrine in November 2015.
Bhowmik led the case that saw nearly a dozen hardliners from the homegrown extremist group convicted for killing the caretaker because they considered him a heretic.
Lawyers in the northern Bangladeshi city have staged protests calling for information about their colleague.
"We are concerned and worried," said Abdul Malek, a lawyer who represented the state with Bhowmik in the trial against the terrorists.
Bhowmik, a Hindu and leading cultural activist, also lead the state's prosecution against five JMB extremists sentenced to death for the murder of 66-year-old Japanese farmer Hoshi Kunio in 2015.
Rangpur regional police chief Khandaker Golam Faruque told AFP that Bhowmik had refused the offer of an armed escort during the high-profile trials.
JMB regrouped after the execution of its founder and top leadership in 2007 and has been blamed for a wave of attacks on religious minorities, atheist bloggers and foreigners in recent years.
In July 2016, suspected JMB terrorists stormed a Dhaka cafe and massacred 22 hostages, including 18 foreigners, in an assault claimed by the Islamic State group.
Bangladesh has been waging a campaign against JMB and other homegrown terrorist outfits in the wake of the attacks.
Security forces have shot dead more than 70 alleged terrorists in a crackdown since the cafe assault.
Hundreds of suspected Islamists have also been arrested, and scores have been sentenced to death.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections. Election results will be out on May 23.