It's been a weekend of huge anti-Japanese protests in as many as 85 cities across China, according to the Kyodo news agency.

Tens of thousands of people took to the streets to denounce Japan's purchase of a disputed chain of uninhabited islands in the South China Sea, prompting the Japanese prime minister to urge China to protect Japanese citizens and companies. This rising tide of anti-Japanese nationalism is now escalating into violence, with some Japanese businesses reporting attacks, while in the southern city of Shenzhen, police were forced to use tear gas, water cannons and pepper spray to disperse the protests.

"Declare war! Declare war!" was the battle cry echoing across one of Beijing's main boulevards, as thousands of protestors marched down it for a second straight day, waving Chinese flags and pictures of Chairman Mao. In a country that does not normally allow protest, the very fact that these protests have been permitted in cities all over China is sending a very clear message.

"The government must support us because the islands are Chinese," says marcher Dong Xiaorong.

Public Anger

There's huge public anger about Japan's purchase last week of the disputed islands, known as Diaoyu by China and Senkaku by Japan. The protesters insist they have taken to the streets spontaneously, but on Chinese microblogs, there are reports of protesters being paid per hour.

Shouting loudly at the head of one column of marchers is Mu Peidong. A young tech-sector worker, he brandishes a homemade sign that reads: "Even if we have to kill all Japanese, we must recover the Diaoyu islands."

He doesn't mince words when asked what he hopes to achieve by marching: "Kick the Japanese out of China! And declare war!" he shouts, "Although China is a peaceful country, our territory cannot be invaded."

As the phalanxes of protesters march, helicopters swoop down low over one of Beijing's main thoroughfares. There are hundreds and hundreds of policemen, anti-riot police and paramilitary troops standing several-deep outside the Japanese Embassy. It's been many years since Beijing has seen demonstrations this large.

Loudspeakers are playing recorded messages urging protesters to respect the law and remain "rational," though many threw water bottles at the Japanese Embassy. Elsewhere, there has been violence. In the southern city of Changsha, protesters brandishing Chinese flags raided a Japanese department store. In Qingdao, a Panasonic electronics factory was completely stripped by looters, and Japanese broadcaster NHK reports that at least a dozen factories were attacked, as well as supermarkets elsewhere.

Japanese Interests Targeted

In Beijing, Japanese restaurants are sticking Chinese flags on their windows, to try to protect themselves from vandals. Even those driving Japanese cars have been targeted, so some drivers have begun pasting signs on their cars declaring that the disputed islands belong to China.

Japanese Prime Minister Yoshihiko Noda has asked China to protect Japanese businesses and citizens.

"Unfortunately, this is an issue that is impacting the safety of our citizens and causing damage to the property of Japanese businesses," he said Sunday.

An article in Sunday's China Daily was titled "Public Anger Grows Over Japan's Provocations."

"Observers described the events as a natural reaction, but cautioned that demonstrators must assert sovereignty in an accepted manner," the article said.

Recent statements by China's foreign ministry spokesman leave no doubt as to its stance,

"China has sacred sovereignty over the Diaoyu island and its affiliated islets," Foreign Ministry Spokesman Hong Lei said Thursday. "The so-called island purchase by Japan cannot change the fact Japan occupied illegally Chinese territory. [The] Chinese people and government are firm and resolute in defending their territorial sovereignty."

U.S. Seeks Calm

The U.S. is expressing unease about the escalation in tensions.

"I am concerned that when these countries engage in provocations of one kind or another over these various islands that it raises the possibility that a misjudgment on one side or the other could result in violence and could result in conflict, and that conflict would then have the potential of expanding," Defense Secretary Leon Panetta said, while en route to Tokyo, after which he will visit China.

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