Four militants were detained after a gunfight between Rapid Action Battalion (RAB) and militants in Mymensingh in early hours of Saturday.
The incident took place in the bank of Brahmaputra at Khagdahar in the city.
A foreign-made revolver and some home-made arms were recovered from their possession.
RAB-14 commander Md Rokanuzzaman said acting on a tip off they conducted a drive in the area. Sensing the presence of them, militants fired on them. In reply, they also fired back. Later, they detained four militants from the spot.