During a joint operation by troopers of Assam Rifles and police, self-styled Lieutenant Salhap Jugli alias Salnang (46) was apprehended from Jongsum village in Kantang circle.
An Italy-made pistol and six rounds of live ammunition were also found in his possession.
According to police, the militant was actively involved in forceful extortion in the district.
On Wednesday, another militant of the organization, self-styled private Bansam Hangphuk (33), surrendered to security forces.