The NIA has filed a charge sheet before a special court here against three NDFB-S militants for their alleged involvement in carrying out an ambush in which two people, including an additional superintendent of police, were killed in 2014, an official said on Saturday.

Bishnu Narzary, Nitul Daimary and Runiluish Daimary have been charged under provisions of the Unlawful Activities (Prevention) Act (UAPA), the Indian Penal Code (IPC) and the Arms Act, he added.

The charge sheet was filed before the Special NIA Court in Guwahati on Friday.

The case relates to an ambush that resulted in the death of Gulzar Hussain, the then Additional Superintendent of Police, Sonitpur, and a civilian, Anlark Basumatary, and injuries to several police personnel in Assam"s Sonitpur district.

The National Investigation Agency (NIA), which took over the probe in the case in August 2019, said members of the National Democratic Front of Bodoland (NDFB-S) had laid the ambush.

Two of the accused named in the charge sheet — Narzary and Nitul Daimary — have been convicted in another case, in which the former has been given a death sentence while the latter has been sentenced to life imprisonment.

Two other NDFB cadres — Kham Kham Daimary and Junu Basumatary — who were involved in the case, were killed in separate encounters with security forces.

Further investigation in the case continues. PTI