Students were on a fourth day of protests, obstructing the road and vandalising vehicles after the deaths of two students in an accident
The incident took place at the Kutubdia Paschim Lemshikhali Government Primary School centre around noon on Sunday.
Supporters of BNP-Jamaat backed candidates tried to raid the centre and snatch the ballot box, said Lemshikhali Union Parishad Chairman Aktar Hossain.
Police fired at them, leaving two injured.
Cox’s Bazar’s Additional Superintendent of Police Tofail Ahmed said additional policemen had been deployed at the centre after the incident.
Earlier, police detained three persons on charges of rigging votes at a centre.
Zafar Alam, Additional Deputy Commissioner (Revenue) of Cox’s Bazar, said reports of sporadic violence were received from many centres.