Cryptocurrencies nosedived on Friday after China’s central bank declared that all crypto-related transactions are illegal and must be banned. “Virtual currency-related business activities are illegal financial activities,” the People’s Bank of China said on its website (via Google Translate). The bank added that digital currencies such as Bitcoin and Ethereum “are not legal and should not and cannot be used as currency in the market.” The announcement caused cryptocurrencies to tumble. Bitcoin dipped by 6%, while Ether plummeted by 10%. The ban is another major step in China’s war on crypto. Chinese authorities have also recently banned banks and payment firms from providing crypto-related services and clamped down on crypto mining. But the announcement that all crypto transactions are illegal may be the biggest threat yet to the industry’s future in China.