An ROC flag spotted among the demonstrators outside the Japanese embassy in Beijing. (Photo/Johnny Lin)

A flag of the Republic of China was waved by protesters outside the Japanese embassy in Beijing on Sep. 15 during a demonstration against the Japanese government's move to nationalize the disputed Diaoyutai (Diaoyu or Senkaku) islands, reports Taiwan-based TV network Eastern Television.

The sight of Taiwan's national flag is extremely rare in mainland China, where the display of emblems of the Republic of China government is banned by the Communist authorities. Despite recent cross-strait rapprochement the flag can only be displayed in museums and Taiwanese goods entering the country must remove national emblems by order of the customs authorities. This is the first time activists have displayed the ROC flag at an anti-Japanese rally in Beijing, though it was also waved alongside PRC flags last month by activists from Hong Kong who landed on the islands in the East China Sea, which are controlled by Japan.

Since the flag disappeared soon after it was spotted, the reason why a demonstrator chose to wave it during the rally remains unknown, though it may represent a call for Beijing and Taipei to work together to reclaim the islands from Japanese control. The demonstration on Saturday was mostly peaceful and no protesters were arrested by the police.

Yelling slogans including "The Diaoyu islands belong to China" and "Go home Japanese," the protesters said that more rallies will be held if the islands are not returned to China. Nearly 500 protesters also surrounded the Japanese consulate in Shanghai, where police demanded demonstrators register their names in order to take part.

Japan's government on Tuesday signed an agreement with the private owners of three of the disputed islands in the East China Sea to buy them for US$26 billion. Japan refers to the islands as Senkaku, while they are known as the Diaoyu in China and the Diaoyutai in Taiwan.