Tensions are running high in Bangladesh after suspected hardline Islamists hacked to death four secular bloggers and a publisher of secular books this year.
Anisuzzaman, a university professor known for supporting secular writers and who goes by one name, alerted police after receiving a death threat via an anonymous text message, a police spokesman said.
"We've provided security to those who've informed us that they're facing security risks," Dhaka metropolitan police spokesman Muntashirul Islam told AFP, adding that police were also acting on tipoffs.
"They must die. Our all Mujahideen, this is our duty to slash their head," the statement said. Some of those named live in Europe.
"We're trying to find out who posted it and from where," Islam said.
Al Qaeda in the Indian Sub-Continent (AQIS) has claimed responsibility for the bloggers' murders. The Islamic State (IS) group said it was behind the recent killings of an Italian aid worker and a Japanese farmer, further stoking concerns of rising Islamist violence in the Muslim-majority country.
