The incident happened at around 10.55 AM when traffic sergeant Manabendro Biswas stopped a motor-cyclist for not wearing helmet on the Dhalai Bridge in the EM Bypass area in Patuli Police Station limits, a senior officer of Kolkata Police said.
The biker, who was later identified as local youth "Pocha" started an argument with Biswas when homeguard Prabir Adhikari intervened to sort out the matter, he said.
The argument in a short span of time turned violent when the biker called up some of his friends from the nearby area, who arrived on the scene on bikes and assaulted both Biswas and Adhikary, the officer alleged.
The police have started a probe into the matter.
