Three more people have been booked in connection with the murder of the Indian National Lok Dal's Haryana unit president Nafe Singh Rathee and a party worker in Bahadurgarh near Delhi, police said on Tuesday.
With this, the total number of people booked in the murder case rises to 15.
A police official said that based on a statement by the INLD leader's son Jitendra Rathee, Vijendra Rathee, Sandeep Rathee and Pale Ram have been named in the FIR.
Rathee and Indian National Lok Dal (INLD) worker Jai Kishan were killed when unidentified assailants sprayed their sports utility vehicle (SUV) with bullets on Sunday.
The attack, which came with less than two months to go before the Lok Sabha polls, drew sharp reactions from the opposition parties in the BJP-ruled state.
In the FIR registered on Monday, police named former BJP MLA Naresh Kaushik, Karambir Rathee, Ramesh Rathee, Satish Rathee, Gaurav Rathee, Rahul and Kamal in the FIR. The report also mentioned five unnamed accused.
The case was registered under various sections, including section 302 (murder), of the Indian Penal Code and the Arms Act.
In his police complaint, Nafe Singh Rathee's nephew Rakesh, said five unidentified killers, who were following them in a car, came out and fired indiscriminately near the Barahi railway crossing.
Haryana Home Minister Anil Vij on Monday said the probe into the killing of the INLD's state unit chief will be handed over to the CBI.
Senior INLD leader Abhay Singh Chautala has accused the BJP-JJP government of failing to provide security to Rathee, despite there being a threat to his life.
