Ryde Mayor Bill Pickering is in hospital after being punched at a polling booth.

Police say the 52-year-old was assaulted at Putney Public school shortly after 2pm by someone known to him who left the school before officers arrived.

Fairfax Media reports that Mr Pickering was handing out ham sandwiches at the by-election polling booth when confronted.

He was treated by paramedics at the scene before being taken to Ryde Hospital.

His condition is unknown.

Investigators are urging anyone with information who has not already spoken to police to come forward.