The Congress on Monday described the killing of Indian National Lok Dal's (INLD) Haryana unit president Nafe Singh Rathee as the state's "first political murder" and demanded a probe into the incident either by a high court judge or a high court judge-monitored CBI investigation.

Senior Congress leader Raghuvir Singh Kadian said Rathee's death was not natural.

"It is a political murder and the first such incident in Haryana after it was carved out as a separate state (in 1966)," Kadian said in the Assembly.

At the beginning of the day's proceedings, the Haryana Assembly paid tributes to former Lok Sabha speaker Manohar Joshi, who died recently.

Chief Minister Manohar Lal Khattar also led the House in paying tributes to Rathee.

While paying his homage, Kadian said Rathee came from a farmer family and rose to become an MLA after a lot of struggle in his life.

Kadian demanded that the culprits behind Rathee's killing be arrested and given exemplary punishment.

"Either a probe by a high court judge or a high court judge-monitored CBI probe should be held into the incident," the Congress leader said.

He said Rathee and he came from the same district -- Jhajjar -- and the slain INLD leader had a keen interest in wrestling and other sports.

Rathee was travelling in a sports utility vehicle (SUV) on Sunday when the assailants, who were in a car, attacked him in Jhajjar's Bahadurgarh town, near Delhi.

Rathee and an INLD worker were killed when the unidentified assailants sprayed the SUV with bullets.

The attack, which came with less than two months to go for the Lok Sabha polls, drew sharp reactions from opposition parties, which alleged a breakdown in law and order in Haryana, which is ruled by the Bharatiya Janata Party (BJP).

Khattar said not a single culprit involved in the case will be spared, adding that police have been asked to arrest the accused as soon as possible and take strictest action.

Senior INLD leader Abhay Singh Chautala accused the BJP-led government of failing to provide security to Rathee, despite there being a threat to his life. He also demanded a CBI probe into the incident.

The Congress and the Aam Aadmi Party (AAP) also hit out at the Khattar government over the incident.

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