Two personnel of the Border Roads Organisation were killed and another injured as NDFB insurgents fired at the personnel in Upper Assam's Dhemaji district last night.
A three-member group of the militants fired at the BRO camp at Sapori between when the BRO staff had retired after dinner, BRO sources said on Tuesday.
One of the ultras, armed with ak-47 rifle waited outside while two others armed with ak-47 and a revolver went in and fired at random firing killing two, operator Pritam Chand from Jammu and Kashmir and Driver Priyam Chand from Himachal Pradesh.
Bhisan Das from Jammu and Kahsmir was injured after being hit by rifle butt, Superintendent of Police KJ Saikia told PTI.
Eight persons have been picked up for questioning.
The NDFB, active in the area, had given an extortion note to the BRO in December threatening to kidnap high officials if its demand was not met, the BRO men in the camp told the SP.
The NDFB had also allegedly demanded Rs 50 from each labourer working in the BRO project but they had paid Rs 20 on Tuesday, according to the BRO men.
Saikia said had the BRO officials informed the police about the extortion note, security measures could have been taken and the incident avoided.
Security around the BRO camp and its other settlements engaged in national highway construction across the state have been stepped up, official sources said.