Two NDFB militants were killed by police in Assam's Karbi Anglong district on Thursday evening, officials said.
Three NDFB militants on a motorcycle hurled a grenade at a police patrol party at Manikpur near Langhin in the district.
Police fired at the militants, killing two of them on the spot while the remaining rebel fled.
A search has been launched in the area and senior police and civil officials rushed to the spot to supervise the operation.
The dead militants were suspected to be behind the killing of two Bodo Liberation Tigers activists in the area a few months ago, police said.