Stock markets across the US and Europe have fallen sharply as fears of a Chinese economic slowdown continue to haunt investors.
Wall Street's Dow Jones was down more than 4% after the first half-hour of trading, having earlier fallen 6%.
London's FTSE 100 index was 4.8% lower in afternoon trade, with major markets in France and Germany down by 6.8% and 5.6% respectively.
The sell-off hit stocks across almost every sector in New York.
The Dow Jones at one point fell below 16,000 for the first time since February 2014, while the technology-heavy Nasdaq index was more than 4% lower in morning trade, recovering a bit after having plunged 8%.
Shares in Asia were hit overnight, with the Shanghai Composite in China closing down 8.5%, its worst close since 2007.
Global investors worry about growth in the world's second largest economy.
China's central bank devalued the country's currency, the yuan, two weeks ago, raising fresh concerns that a slowdown in the country's economy was worse than originally feared.
Currencies and commodities are also falling sharply, because those markets rely heavily on strong demand from China.