BEIJING (NYTIMES) - His nickname in China was "The Cannon," and Ren Zhiqiang's latest commentary was among his most explosive yet.

Ren, an outspoken property tycoon in Beijing, wrote in a scathing essay that China's leader, Xi Jinping, was a power-hungry "clown." He said the ruling Communist Party's strict limits on free speech had exacerbated the coronavirus epidemic.

Now Ren, one of the most prominent critics of Xi in mainland China, is missing, his friends said on Saturday (March 14).

His disappearance comes amid a far-reaching campaign by the party to quash criticism of its slow, secretive initial response to the epidemic, which has killed over 3,100 people in China and sickened more than 80,000.

The Chinese government is working to portray Xi as a hero who is leading the country to victory in a "people's war" against the virus. But many people are still seething over the government's early efforts to conceal the crisis.

Ren, a party member, is well known for his searing critiques of Xi. In 2016, the party placed him on a year's probation for denouncing Xi's propaganda policies in comments online.

The government has monitored Ren's movements ever since, friends said, preventing him from leaving the country and deleting his social media accounts, where he had built a wide following.

His whereabouts was unclear on Saturday, and police in Beijing did not immediately respond to a request for comment.

"We're very worried about him," said Wang Ying, a retired entrepreneur and friend of Ren's. "I will continue to look for him."

In recent weeks, an essay by Ren began circulating among elite circles in China and abroad. In it, he blamed the government for silencing whistleblowers and trying to conceal the outbreak, which began in the central city of Wuhan in December.

While he did not explicitly use Xi's name in the commentary, Ren left no doubt he was speaking about China's leader, repeatedly referencing Xi's speeches and actions.

"I see not an emperor standing there exhibiting his 'new clothes', but a clown who stripped naked and insisted on continuing to be an emperor," he wrote.

Ren, 69, is the retired chairman of Huayuan Properties, a real estate developer.