Guwahati, Nov 19 (PTI): A group of ULFA(I) and NSCN(K) militants today ambushed an army convoy at Pengeri in upper Assam's Tinsukia district, killing three Army jawans and injuring four others seriously.

The group of 15 militants attacked the army convoy early this morning and damaged two vehicles killing one jawan on the spot and seriously injuring six others, a Defence Spokesman told PTI. Two of the injured succumbed to their injuries on way to the hospital, he said.

Tinsukia Superintendent of Police Mugdhajyoti Mahanta said the ambush was carried out jointly by NSCN(K) and ULFA(I) militants carrying very sophisticated weapons including rocket propelled grenade (RPG), AK-47 rifles and mortars.

The security personnel retaliated but the militants managed to escape and it was yet to be ascertained whether there were any casualty or injuries among the militants, Mahanta said.

A huge crater was created at the site of the ambush and two vehicles - a jeep and a Shaktiman truck were completely damaged.

Operations have been intensified in the area with army, police and CRPF personnel surrounding the area and launching massive combing operations. Helicopters have pressed into service for the purpose, the spokesman said.

Home Minister Rajnath Singh spoke to Assam Chief Minister Sarbananda Sonowal and took stock of the situation. Sonowal briefed the Home Minister about the incident, the situation arising of the explosion and the steps taken to nab the culprits.

"I am deeply anguished by the death of Army soldiers in a blast in Tinsukia and prayed for the speedy recovery of the injured," Singh said.

The Assam Chief Minister strongly condemned the incident and directed Director General of Police Mukesh Sahay to rush to spot and review the situation. "We condemn the incident strongly. Operations will be intensified and stern action will be taken against the militants. None will be spared," he said here.

This is the second attack by ULFA(I) at Pengeri in a span of three days. On November 16, a man was killed and two were seriously injured when a vehicle carrying new currency notes to a tea garden for payment of wages to its labourers was fired upon.