While trading and mining of bitcoin and other cryptocurrencies is banned in mainland China, eye-catching adverts for the sector are a common sight in semi-autonomous Hong Kong.

Authorities there have taken steps to regulate the fast-evolving industry in a bid to get ahead of other financial centres such as Dubai and Singapore.

Shares in HashKey Group, which was established in 2018 and runs an exchange alongside other ventures, were trading down 1.95 percent at HK$6.55 (US$0.84) on its market debut, after the group raised US$205 million in an initial public offering.

CEO Xiao Feng hailed the debut as a "glorious day" that showed how "taking the compliant route can also lead to success".

"As entrepreneurs, we come from mainland (China), but HashKey is a homegrown Hong Kong company," Xiao said at its listing ceremony.

"We firmly believe that even in the digital asset industry, a complete set of regulatory rules -- built on centuries of human societal experience -- is essential," he said.

Hong Kong is seen as an experimental field for using cryptocurrencies as mainstream investment tools.

The city launched a licensing system this year for stablecoins, a less volatile type of digital unit.

Virtual currency has been banned in mainland China since 2021, although the country has trialled its own "e-yuan" central bank digital currency.

"China is still quite careful of the use of cryptocurrency," Merton Lam, head of the digital asset firm Crypto HK, told AFP.

So the world's second-largest economy likely sees Hong Kong as "a testing ground" for the technology, he said.

"Crypto is a global thing" and people in Hong Kong can already use major international exchanges such as Binance, but local operators like HashKey can be convenient for those who want to transfer cash into crypto, Lam said.

Etelka Bogardi, a financial technology lawyer at Reed Smith, said the timing was good for HashKey given the "very buoyant IPO market", but the city's crypto-friendly policies had also played a role.

"Hong Kong in particular in the last 12, 18 months has really pushed ahead with a lot of regulations, clarifications, pushes by the administration to make it a more facilitative environment" for blockchain technology, she told AFP.