SINTRA, Portugal (Reuters) - The European Central Bank's president Mario Draghi expressed "sadness" on Monday at Britain's vote to leave the European Union.

In his first comments on the result of last Thursday's referendum, Draghi said: "Sadness is the best word for what we feel when we witness changes of this magnitude."

He was opening the ECB's annual forum on central banking in Sintra, Portugal. Before the vote, Draghi had said the ECB was hoping that Britons would choose to stay.

(Reporting By Francesco Canepa; Editing by Hugh Lawson)