U.S. stocks led a renewed rout in equities worldwide as concern that China's slowing economy will hamper global growth roiled financial markets.

The Standard & Poor's 500 Index swooned into September with its third-biggest loss in 2015 as the beating that erased $5.7 trillion from the value of global equities in August continued. Crude tumbled the most in two months, emerging assets plunged and a measure of risk premium on high-yield debt jumped. Demand surged for haven assets from Treasuries to gold.

The S&P 500 dropped 3 percent at 4 p.m. in New York after plunging 6.3 percent in August for its worst month since 2012. It has fallen 1.1 percent on average in September going back to 1927, the most of any month according to data compiled by Bloomberg.

Asian shares started Tuesday's selloff after a gauge of Chinese manufacturing fell to a three-year low. European stocks followed after a reports pointed to weaker growth in the region, and the slump spread to the U.S. amid data showing the slowest expansion in manufacturing in two years. Treasuries and gold climbed while oil tumbled after entering a bull market. The yen strengthened the most among major currencies.

Trading in U.S. equities has been volatile. Last week alone, the S&P 500 plunged the most since 2011 to enter a correction before rallying more than 6 percent over two days for its best back-to-back gains since the beginning of the bull market in 2009. Selling resumed Monday after Federal Reserve officials signaled they are preparing to raise rates as soon as this month.

The Chicago Board Options Volatility Index jumped 14 percent Tuesday after posting its biggest monthly advance in data going back to 1990.

Stocks in emerging countries also picked up where they left off in August, sliding by 2.4 percent Tuesday. A slowdown in China has repercussions for countries from Brazil to Russia and South Africa, which rely on demand from the world's second-largest economy for exports of goods. The prospects of the Federal Reserve raising interest rates as soon as this month is also weighing on sentiment.

The Fed is scrutinizing data to determine the timing and pace of its first interest-rate increase since 2006. Attention will focus this week on the government's August jobs report, due Friday, as the last major data point before the Fed's meeting on Sept. 16-17.

Boston Fed President Eric Rosengren said Tuesday uncertainty over inflation and global growth justifies a modest pace of interest-rate increases, regardless of when the central bank begins tightening.

Futures traders are betting the Fed will push back a rate increase to later this year. The likelihood they assign an increase in September has fallen to 38 percent, down from 48 percent two weeks ago, according to data compiled by Bloomberg. The chances assume that the federal funds rate will average 0.375 percent after the first hike.

The International Monetary Fund on Tuesday joined private forecasters including Citigroup Inc. and Morgan Stanley in anticipating slower expansion as China's growth weakens and Brazil's economy shrinks.