Keep the seatbelts on.

Stock markets around the world tumbled Tuesday, dashing hopes that financial markets would calm down after two weeks of turbulence.

Investors appear to be growing more nervous about the strength of the global economy. China released a weak report on manufacturing on Tuesday, and an influential international policy maker sounded a downbeat note on the outlook for Asian economies. In early trading on Wednesday, Chinese stocks again fell sharply, leaving the Shanghai composite index 40 percent lower than its recent peak. The price of contracts for the future delivery of oil, an indicator of the course of economic activity, also continued to drop in Asian trading.

In the United States, the Standard & Poor’s 500-stock index slid 58.33 points, or 2.96 percent on Tuesday. The benchmark is now 10.2 percent below its nominal high, putting it back in a correction — the Wall Street term for a decline of more than 10 percent from a peak level. The S.&P. 500 index is still 2.48 percent above the low it closed at last week.

But the underlying ugliness of the action — only three stocks in the S.&P. 500 rose — suggested that the market could have further to drop.