Search operations to track down insurgents continued for the third day on Saturday in and around the area where 18 army personnel were killed in Manipur's Chandel district on Thursday.
Assam Rifles sources said combing operations continued in Paralong, Charong, Moltuh and other areas to track down the insurgents who had launched the biggest attack on the army in two decades, using landmines, rocket-propelled grenades and automatic weapons.
Manipur has been the scene of recurring strife between ethnic and religious groups since Independence. About 2,000 people have been killed in the violence in the state over the past decade, according to the South Asian Terrorism Portal.
The militants may have escaped across a porous border to hideouts in Myanmar, a trek of at least four hours through thick forest from the site of the attack, according to intelligence officers.
The Indo-Myanmar border in that area is largely unguarded with no presence of security forces — either army or paramilitary — at many stretches sometimes running into 10 to 15 km.
Army chief Gen Dalbir Singh had inspected the ambush site on Friday and worked out a plan of action with army and Assam Rifles officers.
The operation involves hundreds of soldiers on foot with the support of helicopters in the remote mountainous forests close to the border with Myanmar, where insurgents are demanding autonomy for their tribal groups or independence, army and intelligence officers said.
The central government asked the army to "trace and eliminate the insurgents" involved in the attack, a military commander said, asking not to be identified.
The militants in Thursday's attack fired rocket-propelled grenades, detonated improvised explosive devices and peppered the trucks with machine guns, army officials said. Two of the military trucks carrying soldiers caught fire.
Three rebels groups active in the area, the National Socialist Council of Nagaland (Khaplang faction), Kanglei Yawol Kanna Lup and Kangleipak Communist Party, claimed responsibility for the attack.
Recently several rebels groups from the region formed a unified group named United National Liberation Front of Western South East Asia.
The central government has handed over the probe into the Manipur ambush to the National Investigation Agency.