The incident occurred at a jungle in the neighbouring country near the Indo-Myanmar border's boundary pillar number two, the sources said.
He was severely injured when a landmine exploded after he accidentally stepped on it, the sources said, adding, the 36-year-old man lost his right leg in the blast.
The two others accompanying him escaped unhurt, the sources said.
The injured, identified as Berona, was taken to the Assam Rifles camp at Parva village, they said.
Efforts were on to take Berona to Lawngtlai district hospital in a helicopter, they added.
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