Sales of Toyota cars in China plunged by 50 percent on-month in September amid an anti-Japan backlash over disputed islands, a report said Friday.

The Japanese auto giant -- the world's largest car firm by sales in the first half of this year -- shifted 75,000 units in August, but moved only half that number last month, the Yomiuri newspaper said, citing a company source.

A Toyota spokesman in Tokyo would not confirm the numbers, saying only that official figures for September sales in China would be released on Tuesday.

A festering row over the Senkaku islands in the East China Sea, controlled by Japan but claimed by China, which knows them as the Diaoyus, has badly affected trade between Asia's two biggest economies.

Japanese factories and businesses across China closed or scaled back operations in September over fears they or their workers could be targeted by mobs protesting against Tokyo's nationalisation of the isles.

Toyota shuttered its factories in the country from September 26 over the heightened tensions, leaving them closed for China's national week celebrations, but will reopen them on Monday, the Tokyo spokesman said.

Late last month both Toyota and its Japanese rival Nissan said they would cut Chinese production because demand for Japanese cars had been hit by the row.

On Friday Jiji news and the Nikkei business daily said Toyota's October production in China could be slashed by about 50 percent from planned levels.

Toyota has nine production sites in China -- three assembly plants each in Tianjin in the northeast, the southern city of Guangzhou and central Sichuan province.

The company has big plans for the growing auto market in China, where it produced 800,000 vehicles in 2011 and maintains a network of 860 dealers.

A report Friday said some big Japanese insurers had stopped providing coverage against riots in China in the wake of last month's unrest, in the latest example of the business knock-on from the dispute.