Near 1550 GMT, US stocks had cut losses a bit, with the Dow Jones Industrial Average down 285.68 points (1.76 per cent) at 15,919.29.
The broad-based S&P 500 fell 33.11 (1.76 per cent) to 1,846.94, while the tech-rich Nasdaq Composite Index shed 93.38 (2.14 per cent) to 4,269.76.
The losses in New York came as European bourses suffered even deeper declines, with London, Paris and Frankfurt all down more than two per cent.
Banking shares were among the worst performers, with Bank of America and Morgan Stanley down more than five percent and Goldman Sachs losing 4.8 per cent.
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Petroleum-linked shares were another hard-hit sector. Anadarko Petroleum lost 4.3 per cent, Marathon Oil 7.7 per cent and Weatherford International 4.3 per cent.
Technology stocks remained weak. Amazon, Facebook and Priceline all lost more than three percent.
Ablin said investors are turning away from the Federal Reserve's interest rate policy and concentrating on corporate performance.
Based on that, there is still a need for a "sizeable" valuation adjustment, Ablin added.