Eight suspected extortionists have been beaten to death in a village in the central district of Faridpur.
Police said hundred of villagers took part in the lynching, but so far there have been no arrests.
One man escaped, but was later arrested. Police said he was found to be in possession of three weapons.
Mob justice is common in Bangladesh, where police are accused of being slow to respond to crimes, particularly in rural areas.
Police said those killed belonged to a gang that had been robbing and extorting money from local people for the last few months.
The gang opened fire on villagers as they tried to escape, officials say.
Police confirmed that the victims were known criminals and some of them were linked to a banned Maoist extremist group.
Hundreds of public lynchings have been carried out in Bangladesh over the last few years.
The government has pledged to bring down crime levels, and even mobilised the army to round up suspects last year.
Correspondents say public lynchings show that the war on violent crime has yet to be won.