Acting on a tip off, an operation was launched in Simlaguri under Amguri Police Station, Assam Police spokesman Rajib Saikia said.
The police team noticed a group of insurgents there at around 4.45 AM and on being challenged, they fired on the security team.
The policemen retaliated the fire, Saikia said.
Later, when the firing stopped, two persons were found injured. The two were taken to hospital where the doctors declared them brought dead, he said.
The two deceased extremists identified as Lukash Narzary alias Langfa and David Islary were active cadres of NDFB(S) and involved in a number of crimes, including extortion, he said.
Operation was continuing to track other NDFB)(S) rebels, he added.