The warning came as Hong Kong-based companies are expected to show the scars of the sometimes violent protests that forced businesses to shut and scared away visitors over the next few weeks when they report their annual results.

"I think local listed companies with local exposure are going to take a very big hit. They already are taking a big hit," Charles Li, CEO of Hong Kong Exchanges and Clearing Ltd (HKEX), told a Reuters Breakingviews event.

HKEX itself posted its steepest profit slide in nearly three years in the third quarter, as investor sentiment was hit by months of unrest that pushed the city into recession for the first time in a decade.

The protests have evolved over the months into a broad pro-democracy campaign, with demands for universal suffrage and an independent inquiry into complaints of police brutality.

Many people are angered by what they see as Beijing's ever-tightening grip on the city that was promised a high degree of autonomy under the "one country, two systems" formula under which it returned to Chinese rule in 1997.

Beijing denies interference in the former British colony and blames the West for fomenting the unrest.

Li said what made Hong Kong great was "one country, two systems", and that he believed China would fundamentally come to the judgement that the two systems worked for the world's second-largest economy, even in the worst case scenario.

HKEX earnings for 2019 are expected to be bolstered by a pick-up in share sales in the fourth quarter, with Chinese e-commerce giant Alibaba raising almost $13 billion from its secondary listing in Hong Kong.

Referring to Alibaba, which in 2013 dropped plans for a primary listing in Hong Kong and turned instead to New York due to rigid listing rules, Li said the exchange needed to eliminate barriers for companies to return.

HKEX launched a surprise $39 billion approach for the London Stock Exchange Group in September, but withdrew it after failing to convince LSE management and investors to back the move.

On potential acquisitions, Li said all options were on the table.

(Reporting by Jennifer Hughes and Anne Marie Roantree; Writing by Sumeet Chatterjee; Editing by Toby Chopra and Alex Richardson)

By Jennifer Hughes and Anne Marie Roantree