The disappearance of Fosun chief Guo Guangchang, dubbed China's Warren Buffett, has stoked fear among captains of industry who thought good behaviour and loyalty could protect them from Beijing's ever-expanding anti-graft campaign.

Guo, the billionaire chairman of Fosun International which is one of China's biggest private conglomerates, disappeared from public view a week ago amid reports he had been detained by police in Shanghai.

As the company's stock tumbled around 10 percent, Guo briefly resurfaced Monday, offering a cryptic reassurance to anxious investors that "there will be a better Fosun next year".

The firm said the 48-year-old executive -- known as a loyal advocate of the ruling Communist Party -- was "assisting in certain investigations" by Chinese authorities, but since then he has dropped out of sight again.

Neither Fosun nor China's authorities will discuss his whereabouts.

The strange episode has had a chilling effect on business leaders who thought Guo's reputation for moral probity and outspoken support for the party was a bulwark against trouble.

"It's definitely scared people. (Guo's) a very highly respected, accomplished figure", said Kellee Tsai, an expert on Chinese business at the Hong Kong University of Science and Technology who is in regular contact with business leaders.

- Clean hands -

Guo's disappearance is not an isolated case in the corruption campaign launched by Xi Jinping after he came to power in 2012.

Other high-profile business leaders have been caught up in the web of graft investigations, which took a new direction after a stock market rout earlier this year that shook confidence in Beijing's ability to manage the country's slowing economy.

Authorities have since focused their efforts on the financial sector, collaring top executives at Citic Securities, Founder Securities and top brokerage Guotai Junan Securities.

Derek Scissors, an expert on the Chinese economy at the American Enterprise Institute, said well-connected tycoons like Guo are "equivalent to senior government officials" in terms of their standing and insight.

"It is not reasonable for Guo or anyone else to think they can't be held for questioning, whether for information they might possess or for 'improper' behaviour, such as an inadequate Party presence in their companies," he said.

"The Party remains compelled to control everything and that certainly includes the 'private' sector."

An avid tai-chi practitioner with a reputation for clean living, Guo had seemed an unlikely target for Beijing's inquisitors.

His disappearance seemed to violate an implicit bond of trust between the government and China's top business leaders whose hard work and financial savvy fuelled China's rise into the world's second-largest economy.

Guo himself said in an opinion piece last year: "As long as you make no mistakes and don't become reckless, the government won't bother you".

But experts say keeping hands clean in China is nearly impossible.

State control over property and industry -- although substantially loosened since market reforms began in the late 1970s -- has made building great fortunes dependent on government cooperation.

"(That) model breeds collusion between officials and business people, and... unavoidably leads to business people being investigated", said Hu Xingdou, an economics professor at Beijing Institute of Technology.

Fosun has a large real estate portfolio in Shanghai -- stronghold of former president Jiang Zemin, whose allies have been targeted by Xi's anti-graft campaign.

Guo was linked by local media to Wang Zongnan, head of state-owned Shanghai retailer Bailian, who was given an 18-year sentence in August for embezzlement and bribery.

The Fosun chairman sold two villas to Wang's parents in 2003 at less than half their market value, according to widely circulated media reports.

Guo denied the allegations, but they raised questions about his relationship with Wang and by extension Jiang.

- Handcuffs the real verdict -

With the authorities remaining mute on Guo's disappearance, there is no way of knowing if it really is linked to Fosun's Shanghai interests.

"(The) impression the Chinese legal system leaves on people is, once you're taken away, (your fate) is essentially decided," said Beijing-based business lawyer Han Bing on social media platform Sina Weibo.

"The presumption of innocence is just writing on a legal document. The police's handcuffs are the real verdict."

That view is leaving executives increasingly concerned about the probes, said Tsai.

"It's not really clear to people what the criteria are for the investigations," she said.

"If I were in that particular cohort of CEOs, I'd be asking myself am I safe? Could I be next?"

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