"Bitcoin presents a number of challenges. The first of them is really the anonymity," Thiam told a results news conference. "I think most banks in the current state of regulation have little or no appetite to get involved in a currency which has such anti-money laundering challenges.

"From what we can identify, the only reason today to buy or sell Bitcoin is to make money, which is the very definition of speculation and the very definition of a bubble."

Bitcoin rocketed above $7,000 (£5,288) for the first time on Thursday, after a more than sevenfold increase in its value since the start of the year.

(Reporting by Joshua Franklin, writing by John Revill; Editing by Michael Shields)