China has detained a well-known Chinese-American microblogger and angel investor as Beijing rolls out a new campaign to "purify" the country's social media, writes Kathrin Hille.
Charles Xue and a 22-year-old woman surnamed Zhang were detained on Friday night for allegedly engaging in prostitution, Beijing police said on Sunday.
Sixty-year-old Mr Xue is one of China's most popular microbloggers with more than 12 million followers on his verified account on Sina Weibo, the country's leading Twitter equivalent.
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Although the authorities made no mention of his frequent liberal comments on social and economic issues, he is one of five prominent microbloggers detained over the past three days.
Mr Xue's lawyer could not be reached for comment.
Charles Chao, chief executive of Sina Corp, which runs Weibo, said in an interview with the Financial Times last week that he believed the government was working to make the Chinese internet a more carefully "managed" space and to come up with new legislation defining more clearly what might and might not be said online.
On Thursday, police detained Qin Zhihui and Yang Xiuyu, the two founders of Erma, a Beijing-based internet public relations company, on charges of creating and spreading rumours. One Erma employee previously worked for a company in which Mr Xue had invested, state media said.
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Liu Hu, a journalist at the Guangzhou-based New Express newspaper, was detained late on Saturday night for allegedly spreading rumors, according to state media.
State media reported on Sunday that Zhou Lubao, a muckraking citizen journalist missing since being questioned by police earlier this month, had been formally arrested for allegedly extorting money from temples by threatening to write scandal about them online.
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"[It is] stupid to make it so easy when there is such an obvious crackdown ongoing and you are front and center in the bullseye already," wrote Bill Bishop, a Beijing-based commentator, on Twitter about Mr Xue.
Hu Xijin, editor-in-chief of Global Times, a Communist party-owned tabloid, said: "You cannot entirely rule out that the authorities are cracking down on Xue Manzi [Mr Xue's web alias] through the whoring charge" as a warning to others who "engage in political confrontation".
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The crackdown has been accompanied by a series of state media reports and commentary calling for stricter regulation of information spread via social media, particularly by celebrity bloggers.
"We should strengthen the positive energy on the net so that when people notice others spreading online rumors [they] call for their removal, like when you see a rat crossing the street," said Liao Hong, president and editor in chief of People.com.cn, the website of the Communist party's mouthpiece. "
Since the launch of Sina Weibo in August 2009, Beijing has tightened censorship online several times in response to the rapid growth of social media as a primary source of and trigger for news, which has put the Communist party's propaganda apparatus on the defensive.
Past measures included a push to enforce real name registration for all Weibo users and a mechanism for reporting rumor-mongering.
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The latest crackdown appears more focused on social media users with big followings and thus the potential significantly to influence public opinion.
"Majority of grassroots celebrity bloggers are PR companies. Big Vs make tens of thousands by retweeting one post," screamed a headline in the Beijing Evening News. "Big Vs" refers to verified microblog accounts with large followings.
According to the Chinese Academy of Social Sciences, among the 30 biggest "internet incidents" in China in 2011 and 2012 there were only 7,584 microblog posts retweeted more than 500 times, and two-thirds of those were posted by just 305 bloggers, highlighting their role as opinion leaders.
"Weibo is absolutely not a completely free space. It has central nodes, the big Vs," said Liu Ruisheng, a media expert at Cass. "The key strategy of people like [Qin and Yang] is to ally themselves with the big Vs and have things retweeted by them."