Chinese protesters smash a Japanese car

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, reports the BBC.

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.

In neighbouring Guangzhou, demonstrators gathered near the Japanese consulate calling on Tokyo to quit the islands.

In Shanghai, protesters held a banner reading "down with Japanese imperialism".

An estimated 200 demonstrators also marched through central Hong Kong to the Japanese consulate chanting anti-Japanese slogans, broadcaster RTHK reported.

In the south-western city of Chengdu, protests shut down a Japanese department store and a branch of the Japanese clothing store, Uniqlo.

The BBC's Martin Patience in Beijing says the outbreak of protests was almost certainly sanctioned by the Chinese authorities, as they were well policed.

In the past, the authorities have used anti-Japanese sentiment to deflect criticism of their rule, he says.

The Japanese launched their flotilla on Saturday, saying they wanted to commemorate the Japanese who died near the islands in World War II.

Early on Sunday, 10 members of the group swam ashore to one of the islets and waved Japanese flags, emulating pro-China activists who had made the same gesture during a previous trip.

One of the politicians on the flotilla, Kenichi Kojima, told AFP news agency: "I want to show the international community that these islands are ours. It is Japan's future at stake."