The Anonymous hacking group claims to have defaced almost 500 websites in China.
Targets hit in the mass defacement included government sites, its official agencies, trade groups and many others.
A message put on the hacked sites said the attack was carried out to protest against the Chinese government's strict control of its citizens.
It urged Chinese people to join Anonymous and stage their own protests against the regime.
The announcement about the defacements was made via an Anonymous China account that was established in March. A list of the 485 sites affected was put on the Pastebin website. Separate Pastebin messages posted email addresses and other personal details stolen when sites were penetrated.
Sites defaced had the same message posted to them that chided the nation's government for its repressive policies.
It read: "Dear Chinese government, you are not infallible, today websites are hacked, tomorrow it will be your vile regime that will fall."
Hello, we are Anonymous.
All these years the Chinese Government has subjected their people to unfair laws and unhealthy processes.
People, each of you suffers from tyranny of that regime.
Fight for justice, fight for freedom, fight for democracy!
In the defaces and leaks in this day, we demonstrate our revolt to the Chinese system. It has to stop! We aren’t asking you for nothing, just saying to protest, to revolt yourself, to be the free person you always want to be! So, we are writing this message to tell you that you should protest, you should revolt yourself protesting and who has the skills for hacking and programming and design and other “computer things” come to our IRC: http://2.webchat.anonops.com/ channel: #GlobalRevolution .
We are Anonymous.
We are Legion.
We do not forgive.
We do not forget.