Stocks ended a turbulent stretch with their worst monthly losses in years, driven by concerns over China and the timing of a U.S. interest-rate increase.

On Monday, the Dow Jones Industrial Average fell 114.98 points, or 0.7%, to 16528.03. The S&P 500 declined 0.8%, and the Nasdaq Composite fell 1.1%.

The Dow lost 6.6% in August, its largest percentage decline since May 2010. The S&P 500 fell 6.3% and the Nasdaq Composite declined 6.9%, the biggest monthly loss on a percentage basis for both indexes since May 2012.

Fears about a slowdown in China have plagued investors for months, weighing on prices of commodities like copper that are dependent on demand from the world’s second-largest economy. Worries were amplified in the middle of August when China unexpectedly devalued its currency, a signal of the government’s concern about slow growth that triggered steep declines in stocks around the globe and further pummeled commodities.

Investors also grappled with the prospect of the U.S. Federal Reserve pushing ahead with raising rates from rock-bottom levels, which have provided support for financial markets across the globe in recent years.