Following an intelligence report in the wee hours of the day, the Army launched operations in Lohit district, which resulted in the four militants being killed.
Three of them were from Nationalist Socialist Council of Nagaland (Khaplang) and the fourth one was from United Liberation Front of Asom, the officials said.
One AK-56 assault rifle and two pistols have been recovered from the slain militants, they said, adding the operation was still underway.