Anti-Japanese protests have taken place in cities across China after Japanese nationalists raised their country’s flag on disputed islands.Thousands of people took to the streets in Shenzhen, Guangzhou and a number of other cities demanding that Japan leave the islands in the East China Sea.In Shenzhen, some demonstrators attacked Japanese restaurants and smashed Japanese-made cars.The islands are known as Senkaku in Japan and Diaoyu in China.Early on Sunday, at least 10 activists swam ashore after a flotilla carrying about 150 people reached the Japanese-controlled islands.Japan’s coast guard is questioning the activists, who had earlier been denied permission to visit the islands.However, as news of the action spread, angry protests broke out across China.In the south-eastern city of Shenzhen, a Japanese-branded police car was overturned and smashed with a metal bar.Footage carried by Hong Kong Cable TV showed other Japanese-branded cars and restaurants being damaged.Protesters waved Chinese flags, burned images of the Japanese flag and shouted slogans denouncing Japan’s claims over the islands."They [Japan] should return the islands to us and apologise,” said one protester quoted by Reuters news agency.