Bitcoin slumped 4.2% to below $50,000, and briefly touched $48,338. It has fallen every day but two since reaching a record high of $64,895.22 on April 14.
While the BOJ currently has no plan to issue CBDC, central banks must not wait idly until the need to roll out its own digital currency arises, he told a seminar.
European indexes enjoyed a much-needed blast upwards -- led by a record close in Frankfurt -- after EU leaders pledged to double vaccine deliveries to 300 million doses between April and June, having been too slow out of the blocks in its immunisation programme.
The dollar index recovered on the day and was last up 0.2pc just short of 90, but remained on track for a fall of 1pc over the week. It had reached its lowest in more than two years at 89.723 on Thursday.