The militant along with two others exchanged fire with the security forces at Kosi bazar area under Serfanguri police station, IGP L R Bishnoi told PTI.
An AK-56 rifle, one magazine, 160 rounds of ammunition, a live grenade, a motorcycle and three mobile phones were recovered from the slain ultra, Bishnoi said.
The extremist was identified as Lakhi Prasad Basumatary alias Laison (27), he said, adding, the two other rebels fled away.