The incident occurred in the afternoon when constable Shantilal Parmar tried to intercept three motorbike-borne youths for a traffic violation, said sub-inspector AK Parmar of City police station.
The youths tried to speed away but their motorcycle collided with an autorickshaw, resulting in injuries to one of the trio, identified as Yogesh Baria.
But Baria alleged that they had crashed into the autorickshaw as the constable had hurled a stick at them.
As word spread of the incident, a mob of around 40 people from the locality nearby to which the youths belonged gathered at the spot, caught hold of the constable and beat him up, the sub-inspector said, adding that they also set Shantilal's motorcycle ablaze.
A case of arson and rioting has been registered following the incident, the sub-inspector said, adding, however, that no arrest has been made so far in this connection.