Microsoft co-founder Bill Gates said that the way cryptocurrencies operate today allows some criminal activities.

After Elon Musk ... Bill Gates reveals his opinion on digital currencies and "Bitcoin"

"It would be good to get rid of that, maybe I should have said biological weapons. This is really bad," the American billionaire added in an interview with The Wall Street Journal published Thursday.

Gates' comments reflect the concerns of some of the most famous investors, analysts and leaders of major financial institutions, who believe that digital currencies are vulnerable to abuse by fraudsters and in money laundering schemes.

In another interview with CNBC, Gates adopted a more moderate stance, describing his views on Bitcoin as "neutral", and said, "I do not own Bitcoin, nor even I bet on its decline, so I took a neutral view."