In a statement the People's Bank of China said the latest notice was to further prevent the risks surrounding crypto trading and to maintain national security and social stability.
Curiously, the statement is dated September 15, but only hit the central bank's website at 5pm on Friday.
Incidentally, the news was already priced in once, with rumors of PBOC crackdown sending the price of bitcoin lower in mid-September when Bitcoin traded just below $50,000.
Naming bitcoin, ether and tether as examples, the central bank said cryptocurrencies are issued by nonmonetary authorities, use encryption technologies and exist in digital form and should not be circulated and used in the market as currencies. The PBOC specifically targeted overseas cryptocurrency exchanges declaring that it was illegal for them to provide online services to residents in China.