Protests against Japan broke out in more than a dozen Chinese cities including Beijing on Sunday, as authorities allowed thousands of people to vent their anger over an escalating territorial row.

The demonstrations -- which saw Japanese businesses, restaurants and cars targeted in some cities -- erupted after Japanese nationalists landed on an island claimed by both countries.

The latest anti-Japan protests are believed to be the most widespread in China since 2005, when several cities saw demonstrations over a slew of grievances including Japan's wartime atrocities.

In the southern city of Shenzhen, which borders Hong Kong, protesters waved Chinese flags and shouted slogans as they marched on major streets, with the numbers swelling to about 1,000, the official Xinhua news agency said.

Protesters overturned a Japanese-made police car and damaged a Japanese restaurant, it said.

Zhang Pei, one of the participants, said protesters were marching towards the train station on the border with Hong Kong.

"The demonstration is strung out for seven to eight kilometres (four to five miles). Many police are escorting us along the street," he told AFP by telephone.

Protests are usually swiftly put down in China, but one analyst said the government had an interest in allowing them to go ahead, for a time.

"They're using the popular card to put pressure on Japan," Willy Lam, a China expert at the Chinese University of Hong Kong, told AFP.

"The (communist) party leadership realises nationalism is a double-edged sword. If they see a possibility of the protests escalating, they will give the signals to put an end to this."

More than 100 people gathered near a complex housing the Japanese consulate in the southern city of Guangzhou, chanting 'Japan get out of the Diaoyu Islands', Xinhua said.

China -- which on Sunday lodged a "strong protest" with Tokyo -- calls the archipelago Diaoyu, but it is controlled by Japan, which calls it Senkaku.

Witnesses said demonstrations also took place in Shanghai and the southwestern city of Chengdu, where protests shut down a Japanese department store and a branch of the Japanese clothing store Uniqlo.

Anti-Japan protests also occurred in Qingdao, on the east coast, as well as in the northeastern cities of Shenyang and Harbin.

Xinhua named several other cities where demonstrations took place, including the capital Beijing.

A demonstrator in Hangzhou, which is close to Shanghai, put the number of protesters there at about 1,000. They marched and chanted slogans before dispersing.

The protests followed the detention of 14 pro-China activists and journalists who had sailed from Hong Kong to land on the islands. They were deported on Friday.

Some Chinese Internet users called on Beijing to take a harder line.

"I've been thinking all the time, where is our mother country at this moment? Where is our army? When can China be tough instead of letting patriots sacrifice?" said a microblog posting by "Mihudemi".

Another, "Li You", said: "What is our government going to do about the Japanese landing on the Diaoyu Islands?" in a posting through the Sina microblog, China's equivalent to Twitter.