China is struggling to restore several government websites that international hacking group Anonymous says it has attacked.

Some of the sites were still blocked Thursday, with error messages shown.

On its twitter account, Anonymous China lists several websites it has hacked belonging to government bureaus in several cities.

Anonymous activists have defaced websites around the world. They are engaged in political causes, including opposition to the global clampdown on file-sharing sites and defense of the secret-spilling site WikiLeaks.

In its message left on one of the hacked Chinese sites, the hackers express anger with the Chinese government for restrictions placed on the Internet.