In the worst such attack in two decades, insurgents on Thursday ambushed a military convoy in Manipur's Chandel district killing at least 18 army personnel and injuring 11 others.
Army and civilian authorities suspect the involvement of Manipur rebel outfit Peoples Liberation Army and Kanglei Yawol Kanna Lup, a Meitei revolutionary organisation, who used landmines, rocket-propelled grenades and automatic weapons.
Prime Minister Narendra Modi condemned the attack as mindless and very distressing.
"Today's mindless attack in Manipur is very distressing. I bow to each and every soldier who has sacrificed his life for the nation," he tweeted.
A team of 6 Dogra Regiment was on a road opening patrol as part of its daily routine along Tengnoupal-New Samtal road, about 80 km from Imphal, when it was attacked by an unidentified insurgent outfit first with a powerful Improvised Explosive Device, a police official said.
After the IED blast, the insurgents resorted to heavy firing at the convoy of four Army vehicles with RPGs and automatic weapons, Army sources said.
"18 armymen were killed and 11 injured in the attack," Army spokesman Col Rohan Anand said in Delhi.
Earlier, Anand had put the number of dead at 20.
A suspected insurgent was also killed, police said.
The attack occurred at around 9 am when the convoy reached a place between Paralong and Charong villages.
"This seems to be the work of PLA, with suspected support by the 'KYKL' group also. We are still waiting for more inputs to come in," Manipur Home Secretary J Suresh Babu said.
However, Army believes that KYKL is behind the attack.
They said that the area of attack is about 15-20 km away from India-Myanmar border.
Defence Minister Manohar Parrikar condemned the deadly attack and said that those who have committed this "cowardly act" will be brought to book, a statement by the defence ministry said.
Union Home Minister Rajnath Singh directed that no militant involved in the attack should be allowed to go scot free and strongest possible action should be taken against all those involved in the ambush.
Defence sources said that that this is the worst attack on the Army in nearly two decades.
"Such ambushes were only heard of in Jammu and Kashmir in mid-90s," the sources said.
A reinforcement party of the security forces was rushed to the spot for combing operation to nab the militants.
The injured have been airlifted to Dimapur in Nagaland for treatment.
Photograph: Representation picture