According to Jorhat Superintendent of Police Sanjukta Parashar, the trio were travelling in car when they were arrested from the heart of the city.
The three have been identified as 'Brigadier' Harmi Muivah, Bibon Agram and Salak Walling.
The police has also recovered one 6 mm pistol, 55 live cartridges and Rs 2.5 lakh cash from them, Parashar said.