The national flag and patriotic slogans cover the outside of a Japanese restaurant in Chaoyang, Beijing. Many Japanese businesses in China closed their doors amid protests against Japan. [Photo: China Daily]

Many Japanese businesses will shut operations on Tuesday, the anniversary of Japan's invasion of Northeast China in 1931, in a precautionary move ahead of possible protests against Tokyo's recent move to "buy" China's Diaoyu Islands.

The worst outbreak of anti-Japan sentiment in decades was seen in protests over the weekend.

Economic and trade ties between the two largest Asian economies are under threat.

Foreign Ministry spokesman Hong Lei said in a daily news briefing that China will protect Japanese firms and citizens and called for protesters to obey the law.

Hong blamed Japan’s illegal purchase of the islands for the "gravely destructive consequences" and said it is Japan that should bear responsibility.

The government has called for the Chinese people to express their demands in a "legal and rational way".

Some Japanese companies closed temporarily, as a matter of prudence.