Ryde mayor Bill Pickering has been knocked unconscious and taken to hospital after tensions erupted at a polling booth for a council byelection on Saturday.

Cr Pickering was handing out ham sandwiches at Putney Public School when he was allegedly confronted by independent candidate Vic Tagg, according to deputy mayor Roy Maggio, who witnessed the incident.

Paramedics treat Ryde mayor Bill Pickering after he was punched at Putney Public School. Credit:Channel Seven

Cr Maggio described the punch as a "king hit" which caused Cr Pickering to fall backwards into a garden bed, at which point he began to have a seizure.

Voting was under way at the time for the East Ward byelection, which was triggered by the resignation in December of former mayor Ivan Petch, who was found by ICAC to have engaged in corrupt conduct.