Major Japanese firms have temporarily shut factories and offices in China after angry protests flared across the country, the result of a territorial dispute that has triggered one of China's worst outbreaks of anti-Japan sentiment in decades.

The row between Japan and China, over a group of uninhabited islets in the East China Sea, has led to violent attacks on well-known Japanese businesses such as car-makers Toyota and Honda, forcing frightened expatriates into hiding and sending relations between Asia's two biggest economies into crisis.

Ratcheting up tensions further on Monday, Chinese state media warned Japan it could suffer another "lost decade" if trade ties soured. Japan exported more than $340 billion last year to China, its biggest single trading partner.

Protests broke out across dozens of Chinese cities at the weekend, some violent, in response to the Japanese government's decision last week to buy some of the disputed islands from a private Japanese owner. The move incensed Beijing.

The protests focused mainly on Japanese diplomatic missions but also targeted shops, restaurants and car dealerships in at least five cities. Toyota and Honda reported arson attacks had badly damaged their stores in Qingdao.

Japanese electronics group Panasonic said one of its plants had been sabotaged by Chinese workers and would remain closed through Tuesday -- a memorial day in China when it marks the anniversary of Japan's 1931 occupation of parts of mainland China.

Tokyo has warned its citizens about large-scale protests in China on Tuesday. Many Japanese schools across China, including in Beijing and Shanghai, have cancelled classes this week.