Acting on a tip-off, a special team of the state police raided Byndihati village in the wee hours and the four were rounded up, district SP Spill Thamar said.
He said during the raid, the militants were trying to smuggle explosives out of the state and the supplier was also arrested.
At least 144 gelatine sticks and 126 detonators were seized from the militants.
Among the militants were self-styled commander of the NDFB-S identified as Bolashi Boro and his deputy Santosh Kharkekary alias K Shimang, he said.