A prominent Hindu lawyer in Bangladesh who fought the state's case in high-profile murder trials against Islamist extremists has disappeared, prompting authorities to launch a massive search operation to trace him.

Ratish Chandra Bhowmik, a leading minority rights activist, went missing after he left his home in northwestern Rangpur district on Friday morning.

When the lawyer did not return home and his mobile phone was found switched off, his family reported about his disappearance to police and Hindu community leaders.

The lawyer's disappearance came a fortnight after seven operatives of outlawed Jamaatul Mujahideen Bangladesh (JMB) were sentenced to death for murdering the caretaker of a Sufi shrine in November 2015.

Bhowmik also appeared as a key prosecutor against five JMB extremists, who were sentenced to death for the murder of a Japanese farmer in 2015.

Bhowmik was also a crucial witness to the trial of senior Jamaate-Islami leader ATM Azharul Islam, who was sentenced to death by a special tribunal for committing crimes against humanity siding with the Pakistani troops during Bangladesh's 1971 liberation war.

Police said that Bhowmik had earlier refused the offer of an armed escort during the high-profile trials.

Bangladesh's elite anti-crime Rapid Action Battalion (RAB) and intelligence agencies have been mobilised to trace the lawyer.

"We have launched a coordinated campaign to trace him...all-out efforts are underway, Rangpur's regional police chief Khondker Golam Faruk said.

Another police official said they have launched the massive search operation in view of possible militant links to Bhowmik's disappearance. "But his professional activities could have earned him enmity of others as well," the official said.

Lawyers in Rangpur staged protests, demanding intensified police action to trace Bhowmik.

Bangladesh has been waging a campaign against JMB and other homegrown militant outfits after a re-grouped faction of JMB called Neo-JMB, stormed a Dhaka cafe in 2016 and massacred 23 people, mostly foreigners.

Hundreds of militants were arrested as part of a crackdown. Many of them have already been sentenced to death for terror attacks.