Two soldiers of Assam Rifles were killed and two others injured on Sunday when militants ambushed a convoy near Jairampur on the Assam-Arunachal Pradesh border, police said.
The attackers belonged to anti-talk faction of the United Liberation Front of Asom (Ulfa) and the National Socialist Council of Nagaland (NSCN) led by Khaplang.
Assam Director General of Police Mukesh Sahay said security forces had launched a counter-insurgency operation against the militants.
Tinsukia Superintendent of Police Mugdhajyoti Mahanta said 15 or 20 militants laid the ambush.
Unofficial sources said the militants fled with some arms and ammunition of the Assam Rifles personnel after the attack.
The Ulfa and NSCN-K ambushed an army convoy in Tinsukia district in November last year and killed three soldiers.