The ultra, who was trying to terrorize people and extort money, was apprehended following specific intelligence inputs by Assam Rifles under the aegis of the Dao Division of the Army, Kohima-based Defence spokesman Col Chiranjeet Konwer said.
A pistol, live ammunition, cash and documents were recovered from his possession.
The ultra confessed that he involved in extortion in Miao area.
Security forces have been carrying out aggressive operations in south Arunachal Pradesh and the netting of the ultra has struck a blow to the extortion activities by the underground cadres of the outfit in the area, the spokesman added.