The three persons were fired upon by the militants when they had gone to fetch water from a reservoir near the barbed wire fencing, IG of Police Control Nepal Das said.
Of the victims, Himari Rangtor (48) was a driver of a water tanker and Jiten Chakma was his assistant. The BSF jawan was escorting them when the firing took place.
Chakma and the BSF jawan succumbed to their injuries on way to the Agartala Government Medical College Hospital here, Das added.