Loni Circle Deputy Superintendent of Police Anil Yadav said the incident occurred yesterday when Sub Inspector Sukhpal Singh and Constable Sanjeev, a part of Leopard Mobile Patrol Party, were trying to decongest a traffic jam.
The policemen warned the fruit vendors to shift their handcarts back to clear the road, following which an argument started between the two sides, Yadav said.
Both police officials nabbed a fruit seller identified as Shahid and asked him to accompany them to the police station.
Upon receiving information, SHO Loni police station Raj Kumar Yadav reached the spot with police force and lathicharged the agitating mob to disperse it, he added.
An FIR has been registered against 21 identified persons and 30 unknown persons for the attack.
Deputy SP Yadav said police is raiding hideouts of the vendors and the culprits will be arrested soon.