"NDFB-S Kokrajhar platoon 'second-in-command' Mithinga and Khuren along with their four associates were arrested from Serfunguri in Kokrajhar district of Assam last night," IGP LR Bishnoi told PTI.
They were accused of massacre of the Adivasis at Pakriguri in Kokrajhar district on December 23.
The extremists led the police to the jungles in Thaisuguri area where they had buried a large quantity of weapons, explosives, medicines and army uniforms, Bishnoi said.
Stating Mithinga and Khuren had themselves fired upon the people at Pakriguri, the IGP said their arrests were a major success in nabbing the perpetrators of the December 23 killings.
At least 81 people, mostly Adivasis, were killed in Kokrajhar, Sonitpur, and Chirang districts by heavily-armed militants belonging to the Songbijit faction of National Democratic Front of Bodoland (NDFB).
Union Home Minister Rajnath Singh had announced while visiting Assam after the killing that NIA would probe into the carnage and the agency has started their investigation.