The incident took place in and around Oting village in Mon district, bordering Myanmar, during a counterinsurgency operation conducted by members of the Assam Rifles, a part of Indian security forces deployment in the state, said a senior police official based in Nagaland.
Firing began when a truck carrying 30 or more coal-mine labourers were passing the Assam Rifles camp area.
"The troopers had intelligence inputs about some militant movement in the area and on seeing the truck they mistook the miners to be rebels and opened fire killing six labourers," the senior police official told Reuters, requesting anonymity as he is not authorised to speak with journalists.