BEIJING, Oct 11 (Reuters) - Japanese automakers Honda Motor Co Ltd (7267.T), Nissan Motor Co Ltd (7201.T) and Toyota Motor Corp (7203.T) saw their sales in China tumble in September as a chip shortage hit vehicle production in the world"s biggest car market. Honda said it sold 121,448 vehicles in China last month, down 28% from a year earlier due to the COVID-19 pandemic and a shortage of components. Nissan said it sold 104,443 cars, down 26%, due to "external headwind including the ongoing pandemic, cross-industry material shortages, slowdowns, and increased competition." Toyota said it sold 115,000 cars, down 36%. Separately, U.S. automaker General Motors Co (GM.N), which only reports quarterly China sales, said it sold over 623,000 in July through September, down 19% from the same period last year, "impacted by the ongoing global semiconductor supply chain disruption." Reporting by Yilei Sun and Brenda Goh; Editing by Christopher Cushing