In a major strike by insurgents, 15 security personnel on poll duty were killed and six others injured in an ambush on a security convoy in Manipur's Bishenpur district on Saturday.

Official sources said 14 security personnel were killed on the spot when about 20 insurgents of an unidentified outfit, hiding on a hill top threw powerful grenades and fired upon a party of the 1st and 4th India Reserve Battalion personnel at Joujangtek area of the district, about 35 km south of Imphal, at around 10 am.

Seven other security personnel were injured by splinters in the heavy exchange of fire between the two sides that lasted for two hours. One of injured later succumbed at a hospital in Imphal. The security personnel led by Commandant D Dhiren were returning in six vehicles to their camps in Churachandpur district after their poll duty at Khoupum polling station in Tamenglong district, the sources said.

Two of the dead personnel were identified as havaldars Jhaljit Singh and Kholi Mao, the sources said. The polling personnel posted at Khoupum polling station had left for Tamenglong district headquarters with election materials, including EVMs by another road.

The EVMs and the election materials were being taken to the office of the deputy commissioner. Earlier reports had said the IRB personnel were escorting polling personnel. The insurgents were reported to have snatched some automatic rifles from the security personnel.

Police and central paramilitary forces rushed to the spot minutes after the ambush was reported to the police headquarters and launched a combing operation. A helicopter was requisitioned to transport the bodies and the injured personnel.

The bodies were taken to the Regional Institute of Medical Science and Hospital for post mortem and the injured to different hospitals in Imphal, the sources said.

All security and police posts were put on alert in the three hill districts of Tamenglong, Churanchandpur, Chandel and Jiribam assembly constituency, which went to the polls in the final phase on Friday.

Reports from Bishenpur district said police and security forces launched a massive manhunt at Joujangtek Hill area to track down the insurgents, whose identity was not immediately known. The area is reportely infested by Manipur insurgents.