Acting on a tip-off about the presence of six members of the Maoist armed wing in a house in remote Deopani Borgora village along Assam-Arunachal Pradesh border, the police cordoned off the entire area, Tinsukia Additional Superintendent of Police Numal Mahato said.
The activists opened fire from inside the house and lobbed a grenade which did not explode. In the exchange of fire that followed, four members were killed while two others managed to escape, Mahato said, adding that a police constable was also seriously injured.
The dead have been identified as head of the rebels' armed wing Siddhartha Buragohain and members Rajeev Gogoi, Arup Chetia and Kamala Buragohain.
The police recovered three AK-47 rifles, a pistol, a grenade, huge quantities of ammunition and several writing pads of CPI-ML.
Search operations were on in the area to nab the two others who managed to escape.
The injured constable, identified as Achinta Das, has been admitted to a hospital in a critical condition.
According to intelligence sources, the Maoists had formed their armed wing recently at Sadiya in Upper Assam, considered its base, and were active along the Assam-Arunachal Pradesh border with efforts to form an armed wing in Lower Assam too.