China Economic fails, Central Bank China (CBC) devalue currency.

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 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.

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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.