Tensions between China and Japan are at their worst in years over rival claims on a group of islands, angry crowds have overturned Japanese cars in one Chinese city and a man ripped the flag off the Japanese ambassador's car in Beijing.

But in shops and department stores in China's main cities, there appears to be no let-up in the purchases of Japanese gadgets, clothing and other products. Even in Nanjing, at the heart of the historic animosity between the Asian giants, it's business as usual.

"I don't like Japan but as the Western saying goes 'politics is politics and economics is economics'," said a young man walking out of an outlet of Japanese electronics retailer Yamada Denki Co Ltd in downtown Nanjing, holding a shopping bag.

"I care more about the quality of the things I buy."

He only gave his family name, Liu, and said he was 27 years old.

Chinese officials and media have fiercely attacked Japan for the dispute over the islands, saying Beijing needs to take a strong stance, including the use of military power if needed. On Thursday, Chinese Vice Minister of Commerce Jiang Zengwei said economic and trade ties could be affected by the row.

China is the world's second-biggest economy and Japan is the third-biggest. Any disruption in their ties could have consequences for the global economy, which has already been buffeted by the debt crisis in Europe and the lack of a cohesive recovery in the United States.

But so far there has been little evidence to suggest such rhetoric is affecting the man on the street. In Shanghai and Beijing, demand remains steady for Japanese goods and merchandise.