The incident took place when the three noticed a packet hung from a tree between Harijori and Bagdoba in the district and one of them brought it down, police said.
Baniram Deka, Deepak Deka and Laganu Kalita suffered serious injuries in the explosion and were shifted to the Guwahati Medical College for treatment.
Police and army personnel have cordoned off the area.
The Assam police had earlier this week sounded a 'red alert' throughout the state in view of the anti-talk ULFA faction's threat to engage in subversive activities in the run-up to the Independence Day celebrations.