A prominent Communist party member who criticised Chinese leader Xi Jinping´s handling of the coronavirus outbreak is being investigated on suspicion of a 'severe violation of discipline and law,' a joint government-party watchdog has said.

Ren Zhiqiang, 69, is a former head of state-run real estate conglomerate Huayuan Group and a party member who has become known for his outspokenness on sensitive topics such as press censorship.

A one-sentence notice issued Tuesday by the party-government joint disciplinary watchdog body in Beijing´s western district said Ren was undergoing a 'review and monitoring investigation' but gave no details and did not mention Ren's article or previous statements.

The ex property mogul dropped from sight in mid-March after publishing an online essay that criticised the leadership´s handling of the virus outbreak that originated in December in central China.

Ren Zhiqiang, a prominent Communist party member who criticised Xi Jinping's handling of the coronavirus outbreak, is being investigated on suspicion of a 'severe violation of discipline and law'. In this file photo from 2012, the then real estate mogul is seen in his office in Beijing

Since taking over the helm of the party in 2012, Xi has shown himself entirely intolerant of any criticism and has cracked down heavily on free media and civil society. He is seen attending G20 Extraordinary Virtual Leaders' Summit on COVID-19 via video link in Beijing on March 26

In March, the Chinese billionaire has allegedly gone missing after calling President Xi Jinping a 'clown' over a speech he made in February about the government's efforts to battle the coronavirus.

Ren Zhiqiang had not been contactable since March 12, three of his friends told Reuters.

'Many of our friends are looking for him,' his close friend and businesswoman Wang Ying said in a statement to Reuters, describing them as being 'extremely anxious'.

'Ren Zhiqiang is a public figure and his disappearance is widely know. The institutions responsible for this need to give a reasonable and legal explanation for this as soon as possible,' she said.

Calls made by Reuters to Ren's mobile phone went unanswered.

People bow in front of Tiananmen Gate in Beijing during a three minute national memorial to commemorate people who died in the COVID-19 coronavirus outbreak on April 4

A man wearing a face mask as a preventive measure against the COVID-19 coronavirus holds a portrait as he stands outside the Biandanshan cemetery in Wuhan on March 31

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.

The article, since deleted by China's censors, is an example of the various criticisms of Xi and the party's handling of the emergency that have appeared online, the one space where Chinese can exercise a modicum of free speech, albeit under the close watch of party monitors.

Criticism has chiefly focused on allegations of early efforts to squelch news of the outbreak, the true numbers of those who have become sickened and died, and efforts by Xi and the party to portray themselves as riding to the rescue when no others could lead China out of the crisis.

Chinese police also reprimanded and threatened a group of medical workers who spread word of the threat early in the outbreak, one of whom, Dr Li Wenliang, later died from COVID-19.

While government data show COVID-19 apparently subsiding in China, more than 1.4 million people have been infected worldwide. A woman wearing a face mask walks at a residential area blocked by barriers in Wuhan, Hubei Province

Ren had an early military career and his parents were both former high officials in the Communist party, leading some to call him a princeling, an often-used reference to the offspring of the founders of the People's Republic - including Xi.

That status might have provided him with some immunity from prosecution, although he appears to have crossed a line by criticising Xi's personal leadership, whether by name or implication.

Since taking over the helm of the party in 2012, Xi has shown himself entirely intolerant of any criticism and has cracked down heavily on free media and civil society, jailing scores of journalists, lawyers and non-governmental activists on labor and other issues.

While government data show COVID-19 apparently subsiding in China, more than 1.4 million people have been infected worldwide.