At least 13 people were killed in a gun-battle between two groups of militants in Manipur's Tengnoupal district on Monday, officials said.
The incident took place at Leithu village on Monday afternoon, they said.
"A group of militants on their way to Myanmar were ambushed by another group of insurgents dominant in the area," an official in the hill district said.
Security forces reaching the spot found 13 bodies so far, he said, adding that their identities were yet to be ascertained but they appeared not to be locals.
Tengnoupal district shares a porous border with Myanmar.