Charles Xue, who has over 12 million followers on the Twitter-like Sina Weibo, was detained on Friday evening in a Beijing neighbourhood along with a woman, according to police and state media on Sunday.
The naturalized American citizen regularly reposts reform-minded content and makes comments on other issues including China's air quality and food safety.
The People's Daily on Monday reminded the country's "big Vs" — popular bloggers whose social media profiles are verified as genuine — that they "should be careful what information they convey ... and use their right to expression responsibly."
Many famous Chinese, from pop stars to business tycoons, have amassed huge followings on social media and at times post material that the government doesn't like, such as calling attention to social injustices and questioning government policies. This month, Internet censors called popular microbloggers to meetings and asked them to agree to standards, including keeping social order, in a move observers have said has a chilling effect on public discourse.
State media have also accused some microbloggers of undermining socialism and promoting Western values through lies and negative news.
Xue's celebrity name, Xue Manzi, shot to the top of the most-searched for terms after his detention was announced.
Among those questioning the motive behind the arrest was the editor of the state-run Global Times newspaper. "Cannot rule out the possibility that authorities are arresting Xue Manzi with a prostitute to give him a hard time," Hu Xijin wrote Sunday in a blog posting that later disappeared.
Referring to Xue, Beijing police announced on their microblog Sunday that a 60-year-old man with the surname Xue had been detained Friday and confessed to visiting a prostitute. It said he had been detained in a Beijing neighbourhood along with a 22-year-old woman who had confessed to prostitution.
Xue's arrest follows a string in recent days of people who triggered scandals online.
On Friday, police detained Liu Hu, an investigative reporter of the Guangzhou-based New Express, who alleged on his microblog that a senior government official was negligent with his public duties. Liu has been arrested on suspicion of fabricating and spreading rumours and the case is being investigated, according to the Beijing police's microblog.
Also detained is a blogger who some call "watch brother" for initiating a campaign against an official who wore expensive watches that he wouldn't have been able to afford on his salary. Zhou Lubao has been arrested on suspicion of extortion, the Ministry of Public Security said Sunday.
Blogger and former journalist Zhu Ruifeng said the detentions were in response to the huge influence some commentators were gaining online, and the fact that more and more netizens were denouncing officials via social media.
Zhu himself triggered a scandal last year when he released online a video of an official having sex with a woman hired by property developers allegedly in an elaborate extortion scheme.
Zhu said Xue's name was all over state media and intended to damage his reputation, showing that the government was serious about controlling online opinion-formers.
AP's Isolda Morillo in Beijing contributed to this report.