The attack on a Assam Rifles convoy in Manipur was not a planned one and happened possibly because the troopers had become "relaxed", Defence Minister Manohar Parrikar has said.In an interview to IANS, the defence minister added that the soldiers retaliated well."This (the attack) prima facie indicates slight relaxation of norms by the troops. SOP (standard operating procedure) was not followed, road opening party was not sent," the minister said."They got relaxed, it was not a planned attack, according to my information, it was a chance attack. But we retaliated well," he added.A junior commissioned officer and five trooper were martyred on Sunday when an Assam Rifles convoy was ambushed in Manipur's Chandel district by insurgents of the Corcom, the apex body of six proscribed underground organisations.The attack reminded of the ambush in the same district last year when at least 18 soldiers were killed when insurgents attacked an Indian Army convoy with improvised explosive devices (IEDs) and rocket-propelled grenades (RPGs).A surgical operation was conducted soon after near India-Myanmar border in which at least two terrorist camps were destroyed. The army did not reveal the number of terrorists killed.