Santanu Bhowmik, 27, was attacked with sharp weapons while covering a road blockade by IPFT.
The CBI has booked three tribal leaders, including a lawmaker, for the murder of television journalist Santanu Bhowmik in 2017, an official said.
The official said that the three were Indigenous People's Front of Tripura (IPFT) legislator Dhirendra Debbarma and party leaders Balram Debbarma and Amit Debbarma, apart from 300-500 IPFT members.
The IPFT is a tribal party and an ally of the ruling Bharatiya Janata Party. It has eight lawmakers in the 60-member Tripura Assembly and two Cabinet ministers in the BJP-led ministry led by Chief Minister Biplab Kumar Deb.
Miscreants allegedly owing allegiance to the IPFT had on September 20, 2017 murdered Bhowmik at Mandwai, 25 km from Agartala. Bhowmik, 27, was attacked with sharp weapons while covering a road blockade by the IPFT, which is demanding a separate tribal state.
IPFT Vice President Ananta Debbarma told IANS that the party will comment later.
A newspaper journalist, Sudip Dutta Bhowmik, was also shot dead inside the Tripura State Rifles 2nd Battalion headquarters at Ramchandra Nagar in West Tripura district on November 21.
The then Left Front government had set up two SITs to probe the two killings.
The SIT arrested four TSR personnel -- including TSR 2nd Battalion Commandant Tapan Debbarma, who is a senior Tripura Police Service officer and was waiting for IPS nomination regarding Sudip Dutta Bhowmik's killing.
The trial in the Sudip Dutta Bhowmik murder case started last month in the West Tripura District Additional District and Session Judge's court but it was stopped following orders by the Tripura High Court.
The BJP-led government told the High Court in May that it had referred the matter to the CBI.