His nickname in China was "The Cannon," and Ren Zhiqiang's latest comment was one of the most explosive so far.

Ren, a Beijing open property tycoon, wrote in a scathing essay that China's leader Xi Jinping was a power-hungry "clown,quot;. He said the Communist Party's strict limits on freedom of expression had exacerbated the coronavirus epidemic.

Mr. Ren, one of Mr. Xi's most prominent critics in mainland China, is now missing, his friends said Saturday.

Her disappearance comes amid a far-reaching campaign by the party to nullify criticism of her slow and secret initial response to the epidemic, which has killed more than 3,100 people in China and sickened more than 80,000.