Northeastern India consists Cause_to_be_included of seven states ( also known as the `` Seven Sister States '' ) : Assam , Meghalaya , Tripura , Arunachal Pradesh , Mizoram , Manipur , and Nagaland .

As of 1 January 2015 , major militant activities are being conducted Action in Assam , Manipur , Nagaland and Tripura .