
China has a strict censorship policy which already applies to popular sites like Facebook and Twitter. China has also blocked a number of Chinese websites that published details of the leak in the Chinese language.
Chinese Foreign Ministry said that the decision to block WikiLeaks was made to ensure China-U.S. Relations were not damaged. The leak revealed that the US Embassy in China knew that that the Chinese government was behind the large scale network hack attempted against some major US corporations including Google as a result of which Google threatened to withdraw from China after the attacks.
Doesn’t look like the Chinese government has blocked the new domain for wikileaks (wikileaks.ch) yet according to this Chinese Firewall Test site:
http://viewdns.info/chinesefirewall/?domain=wikileaks.ch