BEIJING (AP) — China’s central bank has declared all transactions involving Bitcoin and other virtual currencies illegal, stepping up a campaign to block use of unofficial digital money. Chinese banks were banned from handling cryptocurrencies in 2013, but the government issued a reminder this year. That reflected official concern cryptocurrency mining and trading might still be going on or the state-run financial system might be indirectly exposed to risks. The central bank complained Bitcoin, Ethereum and other digital currencies disrupt the financial system and are used in money-laundering and other crime. The People’s Bank of China is developing an electronic version of the country’s yuan for cashless transactions that can be tracked and controlled by Beijing.