An influential Communist Party journal on Monday decried online speech critical of the ruling Communist Party and government, comparing Internet rumours to denunciation posters during Mao Zedong's Cultural Revolution.
"There are some who make use of the open freedom of cyberspace to engage in wanton defamation, attacking the party and the government," said the journal Qiushi, which means "seeking truth" in Chinese.
"The Internet is full of all kinds of negative news and critical voices saying the government only does bad things and everything it says is wrong."
The magazine said online rumours were no better than than "big character posters", hand-written signs put up in public places during the 1966-76 Cultural Revolution to spread propaganda, often denouncing people and institutions as counter-revolutionary or bourgeois.
Qiushi said online rumours, like the posters, were often published under a cloak of anonymity and containing slanderous information. Party leaders have called out for a halt to the posters "resurrecting themselves online", it said.
The Cultural Revolution sought to purge China of what were described as traditional and bourgeois elements and encouraged criticism of those seen as counter-revolutionary or capitalist. Millions were killed, tortured, imprisoned or publicly humiliated during its excesses.
"Big character posters" have also served as vehicles for political expression during other movements in Chinese history.
Internet users can be charged with defamation if postings containing rumours are visited by 5,000 users or reposted more than 500 times, according to a judicial interpretation issued this month by China's top court and prosecutor.
A detained Internet commentator, Chinese-American venture capitalist Charles Xue, admitted to spreading irresponsible posts on Sunday and told state broadcaster CCTV and the official Xinhua news agency that "freedom of speech cannot override the law".
The crackdown on rumours has sparked fears that government regulation will go beyond issues of defamation and clamp down on online speech critical of the government and the party.
"In truth, the work of the Chinese government has received wide praise all over the world, even public opinion in Western countries can't deny that," Qiushi said. "This is a great truth, and overly criticising the government violates that truth."
Sina Weibo, China's version of Twitter, is subject to censorship for sensitive topics, but remains a platform for Internet users to air criticism on political and social issues.