A heavily armed group of United Liberation Front of Asom militants stormed a Central Industrial Security Force camp in Tinsukia district on Friday night in a hijacked Oil India Ltd bus after killing two sentries at the gate.

The militants fought a prolonged gun-battle with CISF jawans in the camp, destroyed an empty crude oil tank and ransacked an office block before fleeing into a nearby jungle, a senior police officer said.

Twelve activists of the banned outfit hijacked the OIL bus, which was on its way to pick up CISF personnel from the Nagajan Oil Circulating Station security camp, just 100 metres from the camp site at around 10 pm.

Militants fired at CISF Havildar Arkan Malai, who opened the camp's gate for the bus mistaking the ULFA activists in military fatigue for security personnel. Malai died on the spot.

Another CISF jawan N Rajbanshi retaliated, but fell to militants' bullets, police said.

The ultras then entered a CISF office block and fired a rocket-propelled grenade at an empty crude oil tank causing extensive damage to it. They later ransacked the office, breaking furniture and telephone sets.

Sixteen CISF personnel, who were asleep in an adjacent room, exchanged fire with the militants, making them flee into nearby jungles.

Massive search operations by the security forces later led to the body of an ULFA militant in the jungle.

Senior police and OIL officials have rushed to the camp.