Dozens of blogs by some of China's most outspoken users have been abruptly shut down in an apparent crackdown.
The move comes amid unexplained changes to popular Twitter-like websites that have users worried the government is trying to restrict them, too. One microblog site is down for maintenance, and the other three now show a "beta" tag as if they are in testing, though they have been operating for months.
The companies that run the websites aren't saying why, fueling suspicions.
China maintains the world's most extensive Internet monitoring and filtering system. Google's refusal to continue censoring search results was one of the reasons it moved its Chinese search engine offshore earlier this year.
Chinese officials fear that public opinion might spiral out of control as social networking — and social protests — boom among the world's largest Internet population, which hit 420 million this year. The government unplugged Twitter and Facebook last year and has kept domestic versions under scrutiny.
The blogs of well-known writers, lawyers and others were shut down abruptly Wednesday on the popular Sohu Inc. portal, which hosts both regular and microblogs.
"I was writing a new post and suddenly my blog couldn't open," lawyer Pu Zhiqiang told The Associated Press.
Legal expert Xu Zhiyong said his blog was also shut down Wednesday, a day after his Sohu microblog was closed. Both men are well-known for taking on sensitive issues.
Blogger Yao Yuan listed at least 61 blocked Sohu blogs, including his own, on a separate, unblocked blog Thursday. He called the closings mass murder.
"If Internet users don't speak out, all sites will be cracked down on in the future," said Yao, who owns an Internet promotion company in Shanghai. "Ordinary people will forever lose their freedom to speak online, and the government can rest without worrying anymore."
More and more bloggers are using microblogs as their primary publishing tool. Microblogs can quickly aggregate critical voices, which is why authorities have been increasing controls, said Xiao Qiang, director of the China Internet Project at the University of California-Berkeley.
"However, given the speed and volume of microblogging content produced in Chinese cyberspace, censors are still several steps behind at this stage," he said in an e-mail.
China's government actually embraced microblogs earlier this year, with the Communist Party newspaper, the People's Daily, launching a microblog of its own.
The People's Daily microblog showed no sign Thursday of new restrictions. Meanwhile, Beijing's public security bureau announced it would set up a microblog for the city's police, the state-run Xinhua News Agency reported Wednesday.
But privately run microblogs are having a tougher time. The Netease.com Inc. microblog is down for maintenance, while the Sina Corp., Sohu and Tencent microblogs display a beta tag.
Sina president Chen Tong responded Wednesday night to speculation that the site could be shut down. "Of course not," he said on the site's microblog. "I've said that sentence more than any other one today."
Government officials could not be reached for comment.
Another possible move against bloggers surfaced this week.
Human Rights in China, a New York-based group, released comments it had obtained by Wang Chen, director of the State Council Information Office, calling for requirements that people use their real names when going online.
"As long as our country's Internet is linked to the global Internet, there will be channels and means for all sorts of harmful foreign information to appear on our domestic Internet," Wang said in April. "Many weak links still exist in our work. These problems have weakened our ability to manage the Internet scientifically and effectively."
Technologically savvy users can still jump China's "Great Firewall" with proxy servers or other alternatives. And they can just keep posting. Pu, the lawyer, said he has already set up a new Sohu blog — his 13th so far.
Associated Press researcher Xi Yue in Beijing contributed to this report.