LONDON - Stocks plunged at the open and stayed down Friday, the day after the United Kingdom’s unprecedented vote to leave the European Union. The outcome of a referendum shocked investors and augured a new era of uncertainty.

At the close of trading, the Dow was down 611.2 points, about 3.4 percent, at 17,399.9. The Standard & Poor’s 500 index gave up 76 points, about 3.6 percent, to 2037.3. The Nasdaq composite lost 202.1 points, about 4.1 percent, to 4,708.

It was the biggest drop for the Dow and S&P 500 since August and the worst fall for the Nasdaq since 2011.

Some European markets fell even more. France’s benchmark index lost 8 percent and Germany’s fell 7 percent. Britain’s fell 3 percent. Bond prices rose sharply as investors sought safety.

The yield on the 10-year Treasury note dropped to 1.57 percent from 1.75 percent a day earlier, a huge move.

The price of U.S. benchmark crude oil was down $2.51 at $47.60 a barrel on the New York Mercantile Exchange. In London, the international benchmark, Brent crude, was also down $2.51 at $48.41 a barrel.

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The pound hit its lowest level since 1985, diving as much as 11 percent before recovering slightly to trade 8 percent lower at $1.3704.

The result of the vote, which trickled in overnight in Europe, caught investors by surprise. Markets had rallied on Thursday on hopes that a so-called Brexit would be avoided and bookies were giving the “remain” camp a high probability of success.

With Newsday staff