The incident took place late last night on the road to Kerapara on the outskirts of Tura, the district headquarters, police said today.
"Four armed militants were killed in the encounter with the special police team, a few km from the district headquarters," West Garo Hills Superintendent of Police Mukesh Singh told PTI.
He said the police team were pursuing the militants who had lobbed a grenade near the petrol pump.
A huge cache of weapons were recovered from the camp that include IEDs, rockets, pistols, automatic rifles and even traditional bows and arrows.
The police said the camp belonged to ANVC-B cadre who fled their camps at Edenbari following a raid last week that left two officers injured.