Calls made by Reuters to Ren’s mobile phone went unanswered.
The Beijing police did not immediately respond to requests by phone and fax for comment on Sunday. China’s State Council Information Office did not immediately respond to a faxed request for comment.
An essay Ren shared with people he knew in recent weeks took aim at a speech Xi made on February 23, which state media reported was teleconferenced to 170,000 party officials nationwide. Copies of his essay were later posted online by others.
In the essay, which does not mention Xi by name, Ren said after studying the speech he “saw not an emperor standing there exhibiting his ‘new clothes,’ but a clown stripped naked who insisted on continuing being emperor,” according to a version posted by China Digital Times, a US-based website.
He also said it revealed a “crisis of governance” within the party, and that a lack of free press and speech had prevented the outbreak from being tackled sooner, causing the situation to worsen.
Ren’s disappearance comes as censorship over how local media and online users discuss the epidemic has tightened in recent weeks.
The coronavirus, which emerged in China late last year, has infected more than 80,000 people in the country, killing 3199.
Ren, who gained the nickname “Cannon Ren” for previous critiques posted on social media, was put on probation from the party for a year in 2016 as part of a punishment for publicly criticising government policy.
That year, the government ordered platforms such as the Twitter-like Weibo to shut down Ren’s social media accounts, which at the time had more than 30 million online followers, saying he had been “spreading illegal information”.
Beijing has framed the battle against coronavirus as a “People’s War” led by Xi.
While the draconian measures to fight the virus, including the lockdown of the city of Wuhan, have proven effective at containing it even as the disease spreads rapidly in other countries, China has faced criticism for suppressing information in the outbreak’s early days.