Thirteen persons were on Monday injured when CPI(M) and Trinamool Congress supporters clashed at Haroa in North 24 Parganas district, police said.
Supporters of the rival parties pelted stones and used lathis in the clash which took place near two polling booths at Brahmanchak area of Haroa.
The area falls under Minakha assembly segment of Basirhat Lok Sabha constituency where polling is underway.
Superintendent of police Tanmoy Roychowdhury clarified there was no firing.
The sub divisional police officer (SDPO) has rushed to the spot and CRPF personnel have been deployed.
The injured were sent to a primary health centre at Haroa, police said.