Major Japanese firms have shut factories in China and urged expatriate workers on Monday to stay indoors ahead of what could be more angry protests over a territorial dispute that threatens to hurt trade ties between Asia's two biggest economies.China's worst outbreak of anti-Japan sentiment in decades led to weekend demonstrations and violent attacks on well-known Japanese businesses such as car-makers Toyota and Honda, forcing frightened Japanese into hiding and prompting Chinese state media to warn that trade relations could now be in jeopardy. "I'm not going out today and I've asked my Chinese boyfriend to be with me all day tomorrow," said Sayo Morimoto, a 29-year-old Japanese graduate student at a university in Shenzhen.Japanese housewife and mother Kayo Kubo, who lives in the eastern Chinese city of Suzhou, said her young family and other Japanese expats were also staying home after being terrified by the scale and mood of the weekend protests in dozens of cities."There were so many people and I've never seen anything like it. It was very scary," she said.Chinese Foreign Ministry spokesman Hong Lei said the government would protect Japanese firms and citizens and called for protesters to obey the law."The gravely destructive consequences of Japan's illegal purchase of the Diaoyu Islands are steadily emerging, and the responsibility for this should be born by Japan," he told a daily news briefing. The islands are called the Senkaku by Japan and Diaoyu by China.