Three Indian soldiers were killed and four seriously wounded on Saturday in a separatist attack in the restive northeastern state of Assam, officials said.

Heavily armed militants of the outlawed United Liberation Front of Asom (ULFA) ambushed an army convoy near the Pengeri reserve forest in the eastern Assam district of Tinsukia, about 550 km (340 miles) from the state's main city of Guwahati.

The ULFA has been fighting for an independent homeland in Assam since 1979. It now operates out of bases in Myanmar, bordering Assam.

"Militants belonging to the ULFA militants attacked the army convoy with rocket propelled grenades, hitting a truck and a jeep. Three soldiers were killed and four critically injured in the attack," Mukesh Agarwalla, Assam’s additional police chief, told Reuters.

The injured were airlifted to a nearby army base hospital with multiple wounds, according to the officials.

"The area is thickly forested and that gave the militants an edge to attack and escape immediately after the strike," an army commander said, requesting not to be identified.

Army, police, and paramilitary troopers have since launched a massive hunt for the rebels and to seal escape routes, an army official said.