Hundreds demonstrated outside the Japanese consulate in the southwestern city of Chongqing this week and burned the Japanese flag. On Sunday, police dispersed a similar crowd in Lanzhou in the northwest.
Many of the demonstrators, as in other anti-Japanese protests elsewhere in China in recent weeks, are young people asserting Chinese claims over islands now under Japanese control. They are known in China as the Diaoyu and in Japan are called the Senkaku.
The protests have been largely peaceful, in contrast to those in 2005, when a few Japanese establishments were attacked. But Chinese security officials have called on people to stay within the law when protesting.
Chung Chien Peng is a political science professor at Lingnan University in Hong Kong.
"After the Tiananmen incident 21 years ago, authorities in China have always been edgy, always been very worried that a crowd of people for whatever purpose could become something bigger, something more violent and could turn against the government. People could start voicing discontent about their own government…. But in the way also, it's very difficult for the government to contain these kind of marches because they (protesters) are doing this for patriotic and nationalistic reasons. And with the latest communication tools, our e-mails, Internet, our cell phones, it's very easy to get a crowd together."
Protests in China are often dispersed quickly, unless they are permitted by local authorities.
Chinese Foreign Ministry spokesman Ma Zhaoxu said Tuesday the protests were "spontaneous acts" against Japan's "erroneous deeds."
The protests were sparked when Japanese patrol boats and a Chinese fishing boat collided in September. Japan detained the Chinese boat captain. Beijing followed by cutting exchanges with Tokyo, and restricting the export of rare earth minerals - which are critical components for Japanese-made electronics. The captain was later released.
Japan occupied parts of China in the 1930s and '40s, killing thousands and subjecting some Chinese to chemical and biological experiments. The memory of that era has been long lasting.
Although tensions have eased in recent weeks, earlier this week Tokyo protested to Beijing over the presence of Chinese patrol boats near the disputed islands, an area believed to be rich in energy resources.
On Wednesday, Chinese officials said Japan needed to take "concrete action" to repair relations. The prime ministers of both countries are to attend the East Asia Summit later this week in Hanoi, but it is not clear if they will hold a bilateral meeting.