SINGAPORE (Reuters) - Cryptocurrencies fell sharply on Friday, with sudden selling dragging bitcoin to a three-week low.

The reason for the drop was not immediately clear. Bitcoin fell as much as 7.7% to $21,404 over a few minutes during the European morning. It recovered slightly and last stood at $22,047. Ether was last down 5% at $1,753.

(Reporting by Tom Westbrook; Editing by Toby Chopra)