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.