SINTRA, Portugal (Reuters) - European Central Bank President Mario Draghi expressed "sadness" on Monday at Britain's vote to leave the European Union, which has roiled global markets and raised questions about the future of the EU.

The Brexit vote has pummeled the pound and hammered banking shares, leaving investors waiting for a response from major central banks.

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."

Draghi, who was opening the ECB's annual forum on central banking in Sintra, Portugal, will fly to Brussels on Tuesday, where he is expected to brief European leaders about the impact of the UK vote on the euro zone at a two-day European Council meeting.

A panel discussion with the heads of the Bank of England and the Federal Reserve, scheduled for Wednesday in Sintra, has since been canceled.

Central banks are ready to cooperate to support financial stability in the wake of Britain's vote to leave the European Union, the Bank for International Settlements said on Saturday, following a gathering of officials in Switzerland.

(Reporting By Balazs Koranyi and Francesco Canepa; Editing by Toby Chopra and Hugh Lawson)