The two sons of slain Indian National Lok Dal leader Nafe Singh Rathee allegedly received threatening calls from an unknown number on Thursday, asking them not to speak to the media about the murder.
A probe has been launched into the matter, the police said.
Nafe Singh Rathee, the president of Indian National Lok Dal's Haryana unit, was shot dead by unidentified assailants in Jhajjar's Bahadurgarh on Sunday.
The deceased leader's nephew, Kapoor Singh Rathee, said that his uncle's elder son Bhupinder and younger son Jatinder have received 18 threat calls from an unknown number.
"The caller also sent us a picture of a weapon which he claimed that he will use to eliminate the family if we do not stop talking to the media," Kapoor Singh Rathee said over the phone from Bahadurgarh.
Bhupinder's wife is a councillor while Jatinder is also a councillor in Bahadurgarh, Kapoor Singh Rathee said.
Earlier on Thursday, Jhajjar police said they were verifying a post on social media, purportedly by UK-based gangster Kapil Sangwan, claiming responsibility for the killing of Nafe Singh Rathee.
Rathee and INLD worker Jai Kishan were killed when unidentified assailants sprayed their vehicle with bullets. The attack, which came ahead of the Lok Sabha polls, drew sharp reactions from the opposition parties in the Bharatiya Janata Party-ruled state.
The Jhajjar police said they are verifying the social media post, purportedly by Sangwan, claiming responsibility for the killing.
The post also claimed that Rathee had a close friendship with Sangwan's rival gangster.
"We are verifying the post and claims made therein," a Jhajjar police official said, adding that so far 15 people have been booked in the murder case.
However, Kapoor Singh Rathee dismissed any gang rivalry angle behind the two murders when asked to comment on the social media post purportedly by Sangwan.
"Rathee sahab had never received any threat from any gang, nor did he have any enmity with any gang or gangster. I think it is a tactic that the accused may be playing to mislead the investigators.
"If one would have noticed the Facebook account was activated barely a couple of hours before the post was uploaded. Hours later, when the post went viral the account was closed," he said.
The police have named former BJP MLA Naresh Kaushik and others in the FIR registered on Monday.
It also mentioned five unnamed accused.
The case was registered under various Indian Penal Code sections, including 302 (murder), 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 Central Bureau of Investigation.
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.
