New Delhi, Mar 6 (IANS): Seven years after the killing of an Additional Superintendent of Police (ASP) in Assam, the National Investigation Agency (NIA) has filed a chargesheet against three National Democratic Front of Bodoland (NDFB-S) militants.

The NIA filed the chargesheet before a Special Court in Guwahati on Friday.

Bishnu Narzary, Nitul Daimary and Runiluish Diamary were named by the agency under charges of Unlawful Activities (Prevention) Act, various sections of the Indian Penal Code (IPC) and the Arms Act.

The case was initially registered on January 28, 2014, at the Dhekiajuli police station in Assam's Sonitpur district in connection to an ambush which resulted in the death of Gulzar Hussain, the then ASP (Sonitpur), and a civilian Anlark Basumatary.

Several other police personnel were also injured in the attack.

The NIA had re-registered the case on August 7, 2019, and took over the investigation.

"The investigation of the case has revealed that the members of (NDFB-S) had laid the ambush which resulted in death of the then ASP and one civilian beside injuring several police personnel," the anti-terror agency said.

Bishnu Narzary and Nitul Daimary have also been convicted in another case wherein the former has been given death sentence and the latter sentenced to life imprisonment.

Two other NDFB cadres, Kham Kham Daimary and Junu Basumatary who were also involved in the crime, have already been killed in separate encounters with security forces.