The army said that it inflicted "heavy casualties" on the insurgent group National Socialist Council of Nagaland-Khaplang during "retaliatory" fire along the India-Myanmar border on the Nagaland side in the early hours on Wednesday.
The Eastern Command of the army also maintained that its troops suffered no casualties during the action.
According to a statement by the Eastern Command, a column of the Indian Army operating along the Indo-Myanmar border was fired upon by unidentified rebels of the NSCN-K around 4.45 am.
"Own troops reacted swiftly and brought down heavily retaliatory fire on insurgents. The insurgents then broke contact and fled from the spot. As per inputs, a large number of casualties were suffered by the insurgents. Own troops suffered no casualties," the statement added.
It, however, did not tell about the number of insurgents killed or injured in the attack.
The army also asserted that Indian troops "did not cross the international border".
Responding to a question at a cabinet briefing abut the incident, Home Minister Rajnath Singh said, "There are no two opinions that Myanmar is a friendly country. Whatever information we get, we will inform you about it."
However, a Facebook post by one Isak Sumi, who is on the 'Most Wanted List' of the National Investigation Agency, said the encounter occurred on the outskirt of Langkhu village located inside Myanmar occupied Naga area, 10-15 km away from Indo-Myanmar border.
"The encounter started around 3 AM when the elite unit of the Naga Army detected a column of Indian Army approaching their temporary make shift camp in the outskirt of Langkhu village located inside Myanmar occupied Naga area, 10-15 kms away from Indo-Myanmar border. The exchange was continuing till the time of filing this report," said Sumi, who is referred to as the PRO of the NSCN by the NIA on its website updated last year.
He claimed that "three Indian soldiers were killed and an unconfirmed number injured but there was no casualty or injury on the Naga Army".
His post states that he is currently based in Yangon in Myanmar and his social media records as also the details on the NIA website state that he belongs to Zunheboto district in Nagaland.
Army sources have maintained that it was "not a surgical strike". Its response came hours after Sumi's post.
The Eastern Command also tweeted, "Reports of casualties to #IndianArmy personnel factually incorrect. Firefight occurred along Indo-Myanmar border at 0445 hrs today @adgpi."
In June 2015, the army had conducted a similar operation against banned insurgent groups following the killing of 20 soldiers in Manipur.
Representational image. Photograph: Parth Sanyal/Reuters