Tinsukia: Suspected militants set ablaze five vehicles and a generator at Tikak west colliery in Tinsukia district on Tuesday night, fired in the air indiscriminately and assaulted a few employees before fleeing into the nearby jungles.

Mining in-charge of ANE Industries Private Ltd at the colliery, Balbir Singh, said around 25 armed militants, split into two teams, attacked the workshop beside the mine around 9.30pm.

"There were around 50 dumpers in service, four of which were parked at the workshop. Over 100 employees were in the mine and the workshop. They fired on diesel and water tanks, hit employees with the butt of their rifles and set on fire five vehicles and a generator. Four dumpers and a service van, valued at over Rs 3 crore, were damaged," he said.

Singh denied having received any extortion demand.

The mine, belonging to North Eastern Coalfields, is located around 7km from Ledo police outpost.

Tinsukia superintendent of police Mugdha Jyoti Mahanta said, "There is no doubt about the involvement of NSCN cadres in the attack. However, we are yet to ascertain which faction was behind the attack and the motive."

The attack is being seen as an attempt by the rebels to encroach Assam land, local sources said.

There have been widespread protests against alleged encroachment by Nagaland in Golaghat and Jorhat districts and against the lack of action on Dispur's part.

The attack is a desperate attempt by NSCN militants to make inroads into Tinsukia district, which had been a stronghold of Ulfa until 2008, the source said.

On December 17 last year, militants had set on fire a dumper and a truck of the same company at Tikak colliery.

The NEC has four other collieries in the area - Tirap East, Tirap West, Ledo open-cast project and Tipong. The last one is non-operational.