The militant was caught from an area under Dhaligaon police station near Aie river late last night, IGP L R Bishnoi told PTI.
The extremist, identified as Thopsa Narzary (28), was involved in the killing of nearly 80 Adivasis on December 23 last year and several kidnapping cases, the IGP said.
One 7.65 pistol, two rounds of ammunition and one grenade were recovered from his possession, Bishnoi added.