Austrian banks should treat cryptocurrency transactions as suspicious until proven otherwise.

The “heightened risk” posed by dealings in virtual currencies like Bitcoin means banks must take extra steps to comply with rules against money laundering, the FMA, Austria’s financial markets cop, wrote in a letter to lenders earlier this year.

“Given virtual currencies’ high degree of anonymity, the risks of money laundering and terrorism financing is elevated,” according to the letter, which was seen by Bloomberg. Banks should “pay special attention and take additional measures if needed to recognize such transactions, validate them and review the origin of the funds.”

Austrian officials including Ewald Nowotny, the country’s central bank chief, have lent their voices to growing global calls for tighter rules on cryptocurrencies. Bank of England Governor Mark Carney said last week that it’s time to end the “anarchy” and “hold the crypto-asset ecosystem to the same standards as the rest of the financial system.”

Authorities in Austria asked Interpol last month to help track down suspects in an alleged scam in which as many as 12,000 Bitcoins, currently worth $138 million, may have been lost.

The recommendations in the FMA’s letter are designed to stop funds from entering the banking system without proper screening under money-laundering rules, and put the onus on Austrian banks to make sure they’re comfortable with their clients’ cryptocurrency business.

Under the guidance, banks should:

• examine whether exchanges with which their clients are doing business are regulated or voluntarily observe rules against money laundering;
• ask clients who receive proceeds from cryptocurrency transactions to provide evidence of how and at what price they obtained the virtual coins;
• end customer relationships if it’s not possible to make the recommended checks.

A spokesman for the FMA confirmed that the regulator issued recommendations to Austrian banks, but declined to elaborate.