BEIJING — Angry anti-Japan protesters took to the streets of Chinese cities for a second day on Sunday, w i th Japan's prime minister urging Beijing to protect his country's companies and diplomatic buildings from fresh assaults over a territorial dispute. In the biggest flare-up in protests over East China Sea islands claimed by China and Japan, police fired tear gas and used water cannon to repel thousands of protesters occupying a street in the southern city of Shenzhen, near Hong Kong. The protests erupted in Beijing and many other cities on Saturday, when demonstrators besieged the Japanese embassy, hurling rocks, eggs and bottles, and testing cordons of police. Demonstrators looted shops and attacked Japanese cars and a restaurant in at least five Chinese cities. Protesters also broke into a dozen Japanese-run factories in the eastern city of Qingdao, according to the Japanese broadcaster NHK. “Regrettably, this is a problem concerning the safety of Japanese nationals and Japan-affiliated companies," Japanese Prime Minister Yoshihiko Noda told a talk show on NHK. “I would like to urge the Chinese government to protect their safety." The protests, the latest setback in long-troubled relations between Beijing and Tokyo, followed Japan's decision on Tuesday to buy the disputed islands, which Tokyo calls the Senkaku and Beijing calls the Diaoyu and which could contain valuable gas reserves, from a private Japanese owner. Beijing called that decision a provocative violation of its sovereignty. China is struggling to find a balance between venting public anger against Japan and containing violence that could backfire ahead of a delicate leadership succession. “China has a lot of problems, but Diaoyu is one thing that everyone in this country agrees on," said He Guoliang, 26, part of a smaller crowd that resumed protesting in Beijing Sunday. “There are some lines you don't cross." A six-deep cordon of anti-riot police guarded the Japanese embassy in Beijing as demonstrators, some throwing water bottles, resumed their protest on Sunday. “If Japan does not back down we must go to war. The Chinese people are not afraid," said 19-year-old-student Shao Jingru. “We are already boycotting Japanese goods," he said. “The government should adopt sanctions on Japan, increase duties on their goods to show them that we are serious." Police used loud speakers to tell protesters they should respect the law. Another protester, a student named Xia Zhelin, said: “Our patience with Japan is exhausted." In Shanghai, about 1,500 people marched towards the Japanese consulate, where they were allowed to enter cordoned-off areas in small groups. Protesters carried flags and images of late Communist leader Mao Zedong as hundreds of police looked on. Police headed off a crowd of at least 2,000 protesters who were trying to charge into the US consulate in the southwestern city of Chengdu. Protesters said they wanted the United States “to listen to their voices". The Nikkei business newspaper said Sunday demonstrators had earlier attacked two Panasonic electronic parts plants in the eastern cities of Qingdao and Suzhou. The company will decide whether to continue operations after checking the damage. Toyota vehicle dealerships were also set on fire and many vehicles were damaged, it said, citing Toyota's China unit. Tong Zeng, a businessman in Beijing and president of the China Federation for Defending the Diaoyu Islands, said these were the most widespread protests against Japan he had seen and that the protests reflected pent-up social frustrations. “Some ordinary people have a kind of blind hatred of Japan, and as soon as you mention Japan they will show that," he said. The flare-up has come while Asia's two biggest economies focus on domestic political pressures, narrowing the room for diplomatic give-and-take. Noda's government faces an election in months, adding pressure on him not to look weak on China. The ruling Communist Party is preoccupied with a leadership turnover, with President Hu Jintao due to step down as party leader at a congress that could open next month. While the public indignation against Japan could help to foster unity, it has also exposed widespread public impatience for a tougher line from Beijing. — Reuters