Angry protesters have staged sometimes violent anti-Japanese demonstrations in cities across China, amid escalating tensions over disputed islands in the East China Sea.
In Beijing, protesters threw stones and bottles and tried to breach a barricade manned by riot police.
There were reports of protests in at least 11 other cities.
Passions have been inflamed by the purchase of some of the islands this week by the Japanese government.
China briefly sent six surveillance ships into waters around the islands on Friday.
It was responding to Tokyo's announcement that it had bought three of the islands from their private Japanese owners.
BBC Asia-Pacific analyst Charles Scanlon describes the purchase as an attempt at damage limitation following a much more provocative purchase plan by the nationalistic governor of Tokyo, who wanted to develop the islands.
Japan controls the resource-rich islands, known as Senkaku in Japan and Diaoyu in China, and which are also claimed by Taiwan.
In Beijing, hundreds of protesters tried to storm a barricade but were pushed back by riot police with batons and shields.
"Return our islands! Japanese devils get out!" some shouted in Beijing, reported Reuters news agency.
In Shanghai, the scene of recurrent anti-Japanese protests, the police allowed only small groups of protesters to approach the Japanese consulate.
Protesters elsewhere attacked Japanese restaurants and in one place overturned a Japanese-made car, said reports.
The dispute has been ratcheted up by the media in both countries - in China, where a leadership change looms and in Japan, in the run-up to an election.
Diplomats on both sides recognise that they have much to lose, but nationalistic passions are hard to contain, says the BBC's Asia-Pacific analyst Charles Scanlon.
"I think the government is encouraging this," one protester in Beijing, who gave his name as Uda Chen, told Reuters.
"They could have stopped all of us approaching when we were at the subway station. The government has taught us to be anti-Japanese at school, so if they want us to stop it would be like slapping their own mouths," he added.