The militants hurled a grenade at the security forces at Laijanguri, under Rangapara police station, and in the ensuing encounter two extremists were injured, the sources said.
Operations were on in the area against the National Democratic Front of Bodoland insurgents, the sources said.
The NDFB-S had unleashed violence in the twin districts of Baksa and Kokrajhar since May one killing 32 persons, injured several others and rendered thousands homeless.