Five policemen were killed when ULFA militants hurled a grenade at the convoy of a senior police official on Friday.
The militants attacked the three-vehicle convoy of Tinsukia Superintendent of Police Debojit Hazarika at Pengeri.
Hazarika is safe but five policemen were killed in the attack, official sources said.
The grenade had hit the vehicle of Margherita Sub-Divisional Police Officer Sujit Thakur, but he escaped unharmed as he was travelling in the SP's vehicle.
An encounter ensued as the policemen retaliated by opening fire and patrolling security personnel from the nearby areas rushed to the area.
ULFA has stepped up violence in the run-up to the Independence Day celebrations in the state.