Beijing-based microbloggers on Friday will be prevented from registering an account on one of the country's hugely popular Twitter-like services in anything but their real name, verified by their national ID card.
The move has been slammed by netizens and rights groups alike as a huge blow to freedom of expression in China, where many rely on services like Sina Weibo to find news and views that have been censored out of the tightly controlled state media.
"The microblog revolution, sharing of opinions, and increased circulation of news resulting from microblogs have led the regime to take certain measures," the Paris-based press freedom group Reporters Without Borders (RSF) said in an annual report this week.
"The police accused Chinese Twitter of having a 'bad influence on society,'" the group said in the report which once again designated China as one of the world's "Enemies of the Internet."
The moves come after major Chinese Internet service providers like Sina, Baidu, and Tencent agreed with the government last November that they would implement its directives on online surveillance.
"These businesses promised to combat online pornography, Internet fraud, and the dissemination of rumors and false reports," RSF said.
Under the rules issued by Beijing's municipal government in December, users must link their mobile phone numbers to their Weibo account and only those verified will be allowed to post messages.
While Sina has said the regulations will hurt its business, the company expects that around 60 percent of users will have complied with them by Friday's deadline.
Computer expert Ye Yun said the government has continually sought ways to limit freedom of expression on the Internet since people started using it, and that the real-name system for social media was only the latest step in that process.
"Online news sites have no permission to carry out their own reporting; all they can do is edit and repost things," Ye said. "Most [news] comes from a small cluster of large portals, so the content on the Web was being created by netizens themselves."
"But it will be very hard to continue doing it this way under such a concerted effort to control it," he said.
"The real-name system is their way of adapting to this [trend]."
Of China's 513 million netizens, around half access the Web via their mobile phones, and around 250 million have microblog accounts.
However, authorities have recently detained a number of netizens and online editors over retweeted material that was controversial, under new guidelines aimed at preventing the spread of online "rumors."
Earlier this month, authorities in Guangdong province detained Web forum editor Shang Laicheng after he reposted an Internet forum message alleging that local prosecution officials had used the services of prostitutes.
Shang is now the subject of a police investigation and has been placed on leave from work for passing on a message posted by another person on the company's forums.
Li Yizhong, former director of China’s Ministry of Industry and Information Technology (MIIT), defended the government's move in an interview with the Beijing Times newspaper this week, saying that real-name registration happens in other countries, too.
"The trials with real-name registration on the Weibo are for the sake of the orderly and healthy development of the internet—in order to protect the privacy and secrecy of individuals, corporations, and the nation," Li told the paper in an interview translated by the Hong Kong-based China Media Project.
The Hong Kong-based China Human Rights Defenders (CHRD) group has hit out at the new controls, calling them "the most alarming development" on the Chinese Internet during 2011.
"The thriving domestic microblogsphere has proved highly effective in exposing government misconduct during the past few years, but it is now threatened with curtailment as a result of this requirement," the group said in its annual report last week.
"Since the two main internet companies operating microblogs in China—Sina and Tencent—are based in Beijing and Shenzhen, the new measure is likely to affect most of China’s 250 million registered microblog users," the report said.
"Microblogs are operated by several giant Internet companies who have a strong track record of avoiding trouble by complying with censorship requirements," CHRD said.
Reported by Xin Yu for RFA's Mandarin service. Translated and written in English by Luisetta Mudie.