Three policemen were injured in the gunfight that erupted when police tried to arrest them, reports UNB.
The arrestees are - Akash Mollah, 21, resident of Katarbil area of the upazila, Md Habib Ullah, 19, Kabirul Islam, 26, of Nazirpur upazila, and Mizanur Rahman, from Mathbaria upazila of Pirojpur district.
There was information that a gang was on a sabotage plan and a team from Kachua police station raided an abandoned house of one Safayet Sheikh at the village around 3am, said Bagerhat Superintendent of Police Pankaj Chadra Roy.
Sensing the presence of police, the militants opened fire at them, prompting them to retaliate that triggered a gunfight.
Later police arrested the four while others managed to flee the spot.
One revolver, two rounds of bullets, five crude bombs and some bomb making materials were discovered in the house, the SP also said.