A key test of their unity would be on Sunday, at a protest rally in Delhi to which AAP has invited all opposition parties
The attackers struck in a remote and forested area of Sukma district in Chhattisgarh state on Saturday, the inspector general of the state's police force, P Sundarraj, said.
"There was a heavy exchange of fire," he told Reuters
The far-left guerrillas have been fighting in eastern, central and southern forest areas since the 1960s, demanding more rights for the poor and for tribal groups.