The Financial Stability Board, which is affiliated with the central bank, said interest in virtual currencies from the public had lately increased "very much" and particularly as an investment opportunity. It gave no further details.

"Investors in virtual currencies ... have to take into consideration whether risks are in line with their personal preferences and investment goals," the board said in a statement.

Bitcoin, for example, enables individuals to transfer value to each other and pay for goods and services bypassing banks and the mainstream financial system.

Last month, European Central Bank President Mario Draghi criticised a proposal by the Estonian government to launch a state-managed digital currency, saying the euro was the only valid money in the euro area.

Estonia became the first European country to openly discuss the prospect of a digital currency managed by the government and offered to the country's more than 20,000 e-residents - foreign entrepreneurs who open a firm in the country via the web.

The Financial Stability Board, which consists of representatives of various government bodies, is headed by the Bank of Slovenia Governor Bostjan Jazbec, who also sits on the ECB's governing council.

The board is responsible for implementing macro prudential policy that would protect the stability of Slovenia's financial system.

The statement also said that initial coin offerings (ICOs) are also not regulated and controlled, and said investors in ICOs should invest "in the amount that would not leave them too exposed".

ICOs have been used by digital currency entrepreneurs around the world to raise large sums quickly by creating and selling digital "tokens" which have no regulatory oversight.