A group of heavily armed KPLT ultras stormed the project site, about 34 km from here, under Manja police station, and took hostage 11 labourers, engaged by P Das and Company.
The militants released four of the labourers after they identified themselves as Karbis and took away the remaining labourers.
Senior police officials have rushed to the spot. A massive search operation have been launched to rescue the abducted labourers.
Work on the Longlit hydro-power project was started in 2006 and was expected to be completed by 2010 but it has been delayed due to militant threats, sources said.