SYDNEY, July 21 (Reuters) - Australian retail sales slumped in June as a coronavirus lockdown in the southeastern state of Victoria and mobility restrictions in the country’s most populous city of Sydney hit demand, preliminary data showed on Wednesday. Retail turnover in June fell 1.8% from a month earlier, the biggest drop this year, according to figures from the Australian Bureau of Statistics (ABS). Median forecasts of economists polled by Reuters had pointed to a 0.5% fall in June. Final results will be released on Aug. 4. (Reporting by Swati Pandey; Editing by Jacqueline Wong) Our Standards: The Thomson Reuters Trust Principles.