Sub-Inspector Shahdara Khan and Assistant Sub-Inspector Hafi and an operative known as Sagir suffered bullet wounds in the gunfight that rocked the village predominantly of Jamaat adherents in Satkania upazila, 48 kilometres off the port city.

Among the arrestees, Mohammad Monzur identified himself as the nephew of Shahjahan Chowdhury, local lawmaker of the ruling coalition partner Jamaat-e-Islami, sources said.

The firefight came at about 11:00am three days after joint forces seized the largest ever arms haul in Chittagong on Friday exposing the region as an easy route for gunrunning.

"Police cordoned a hilltop garden on secret information and the area reverberated with a hail of bullets," a police officer said.

Witnesses said police arrested the four in retreat after the gunfight that continued for an hour amid an exchange of several hundred bullets.

Police named other arrestees as Mohammad Garun, Mohammad Lokman and Mohammad Sagir, who were preparing for an apparent robbery in the neighbourhood.

The seizure includes an AK-47 rifle, a foreign-made pistol, four magazines of AK-47 rifles and 325 bullets.

The gunfight triggered tension in the area and led police to tighten security and raid suspected hideouts to arrest other operatives who fled the scene.