NEW YORK — Investors began giving in to fears Thursday that a global recession is already under way, and stock markets shuddered around the world. Selling started in Asia, picked up speed in Europe and sent Wall Street near its worst finish of the year.

The Dow Jones industrial average lost 391 points and at one point was down more than 500, a return to the volatility that gripped the market this summer.

One financial indicator after another showed that investors are losing hope that the global economy can keep growing. The price of oil and metals such as copper, which depend on economic demand, fell sharply. Traders bought Treasury bonds and the dollar for safety.

FedEx, a company that ships so many goods that it is considered a barometer of the U.S. economy, had to lower its earnings forecast for the year because customers are putting off purchases of electronics and other gadgets from China.

The Dow fell 391.01 points, or 3.5 percent, and closed at 10,733.83. The selling was not just steep but broad: Nineteen stocks on the New York Stock Exchange fell for every one that rose.

'Markets rely on confidence and certainty. Right now there is neither,' said John Canally, an economic strategist at LPL Financial, an investment firm in Boston.

It was the second consecutive rout in the stock market since Wednesday afternoon, when the Federal Reserve announced a change in strategy for fighting the economic slowdown — a bid to lower long-term interest rates and get people and companies to spend more money.

Economic news was bad around the world. A closely watched survey in Europe indicated that a recession could be on the way there, and a manufacturing survey suggested a slowdown in China, which has been one of the hottest economies.

'The probability of going back into recession is higher now than at any point in the recovery,' said Tim Quinlan, an economist at Wells Fargo. He put his odds of a recession at 35 percent.

Christine Lagarde, the head of the International Monetary Fund, said the world economy was 'entering a dangerous phase.' She told an annual meeting of the IMF and World Bank that nations need credible plans to get their debt under control.

In the U.S., investors poured money into American government debt, which they see as less risky than stocks. The yield on the 10-year Treasury note hit 1.71 percent, the lowest since daily record keeping began half a century ago. It was 3.66 percent as recently as February.

Yields fall as investors buy bonds and send their prices higher. Small yields are a sign that investors are just looking for a safe place to park their cash.

The Dow almost matched its lowest close of the year, 10,719 on Aug. 10.

The Standard & Poor's 500 index, a broader measure of the stock market, and the Nasdaq composite, which is more heavily weighted with technology stocks, both fell more than 3 percent for the day.

'They want to get their money back,' said Guy LeBas, chief fixed income strategist at Janney Capital Markets. 'How much they earn is secondary.'