Large political protests in China are a rarity and even planning a march can lead to jail-time. As a result, the series of anti-Japan demonstrations in China over the last two weeks has prompted suspicion the government was working behind the scenes to promote the protests.

Yet with the latest round of marches over the weekend, including an occasionally violent, 20,000-strong demonstration in Shanghai, the perception is growing that the anti-Japanese sentiment might be slipping out of the government's control.