The 18 Army soldiers who were killed in Manipur belonged to the 6 Dogra infantry regiment.
The Indian Army, in a joint operation with the Air Force, engaged groups of militants at two locations inside Myanmar on Tuesday and said it had inflicted "significant casualties." Initial reports suggest that about 50 or more militants have been killed in the operations.
Sources said among the militants killed are those behind last week's ambush of an Army convoy in which 18 soldiers were killed in Manipur's Chandel district, the deadliest attack on security forces in two decades.
Starson Lamkang of the National Socialist Council of Nagaland or NSCN(K), who is suspected to have played a key role in organising the June 4 ambush, is reportedly injured in today's operations.
Prime Minister Narendra Modi had given the go ahead to the Indian Army for "hot pursuit" of militants into Myanmar in which two militant camps were completely annihilated, Union Minister Rajyavardhan Singh Rathore disclosed today. "Its become a habit for these militants to strike at the Indian Army or paramilitary forces or citizens and then cross over into safe havens being confident of the fact that Indian Armed forces will not pursue them," he told NDTV.
"This message is now very clear for all those who harboured intentions of terror on our country," he said.
Mi-17 helicopters of the Air Force were deployed and, sources said, the Assam Rifles and the Army's Special Forces - 21 Para (SF) - carried out surgical strikes inside Myanmar, where the militants had fled to, entering about 2 km into the neighbouring country, something that was not confirmed by the Army.
Major General Ranvir Songj said today's operations followed "very credible and specific intelligence" that the militants were planning to carry out more attacks.
Sources said the operations took place in Ukhrul, Manipur, and in Tuensang district of Nagaland, where a mixed group of militants attempted to infiltrate into India.
Militants belonging to People's Liberation Army (PLA), United National Liberation Front (UNLF) and Kanglei Yawol Kanna Lup (KYKL) have been killed.
The Army has said it is "in communication with Myanmar authorities and look forward to working with them to combat terrorism."