China's central bank is "quite worried" about risks to the global financial system from private digital currencies and has taken some measures, said Fan Yifei, vice governor the People's Bank of China (PBOC), at a media conference in Beijing on Thursday.

Digital currency issuers can be private issuers or central banks, Fan said. The typical representatives of private digital currencies are currencies such as bitcoin, as well as various so-called stablecoins.

"These currencies have become speculative tools, bringing potential risks to financial security and social stability," Fan pointed out. 

Meanwhile, these currencies have themselves become payment tools for money laundering and illegal economic activities, he added.

"Some commercial organizations' so-called 'stablecoins,' particularly the global 'stablecoins,' are likely to bring risks and challenges to the international monetary system, and payment and settlement system," Fan said. 

The central bank is still observing and studying whether the private digital currencies exist as monetary credit or not, according to Fan.

On Tuesday, a department of the PBOC ordered the shutdown of a Beijing-based software maker over its suspected involvement in cryptocurrency trading.

In May, China launched a national-level scrutiny on cryptocurrencies, vowing to crack down on all bitcoin mining and trading activities to prevent financial risks. 

China is accelerating its national rollout of its central bank digital currency (CBDC), e-CNY or digital yuan. It has carried out trials on the currency in about a dozen regions within the country since last year.

Fan said the CBDC China is promoting consists of two types: the wholesale CBDC and the retail CBDC. The former is mainly issued to institutional entities such as commercial banks and is mostly used for large-value settlements, while the latter is mainly issued to the public and can be used for daily transactions.

Most studies believed that the wholesale CBDC will not have an impact on the existing financial system but diverged in terms of the retail CBDC, Fan said, adding that the bank is highly concerned about financial impacts of the retail CBDC.

"We are currently in the process of piloting [and] will strive to ensure that the impacts of the digital yuan on macro aspects can be minimized through business, technology and policy design," he said.