Masroor Ali Siyal, a leader from the ruling Pakistan Tehreek-e-Insaf (PTI) party, and Karachi Press Club President Imtiaz Khan were among the panellists on the show "News Line with Aftab Mugheri".
In a video apparently shared by the journalist, Siyal is heard warning Khan about his tone and tenor.
Khan replies in a high-pitched voice that he too won't tolerate any nonsense.
Within a split of a second, Siyal gets up and violently pushes Khan from the chair. And then, in a fit of rage, he clutches Khan with his arms -- like in a wrestling bout -- and apparently hurls blows at him.
Both shout and swear at each other, shocking the moderator. The two were later separated by other guests on the show and the crew on the set.
Siyal returns to his chair while Khan walks out of the studio. After some minutes, Khan returns to the show and again sits next to Siyal, warning the PTI leader of legal consequences over the incident.
The video has become a rage on Twitter and within hours had been viewed by 99,000 people. Many trolled the politician over his conduct on a live TV show, and one tweet referred to the incident as an outcome of "Naya Pakistan".
Freelance journalist Naila Inayat said, "Is this Naya Pakistan? PTI's Masroor Ali Siyal attacks president Karachi press club Imtiaz Khan on live news show."
Wasay Jalil, member of the 'Voice of Karachi', a US-based advocacy group for the rights of Urdu-speaking people of Karachi, wrote, "Few days back #PTI 's Fawad Ch slapped Sami Abraham & now Dr Mansoor Sial thrashing Sr Journalist Imtiaz Faran in a talk show in Karachi."
Jalil captioned his post saying, "Unbelievable!!!!"
(With inputs from IANS)