Global stock markets fell around the world as concerns about the US-China trade war and the global economy prompted investors to dump shares.
The three main US stock markets closed 3% lower overnight, European stocks fell across the board, while Asian stock markets opened lower.
Weak data from Germany and China on Wednesday helped fuel a rush for safe assets like bonds and gold.
Bond market moves pointed to possible recessions in major economies.
The US central bank also came under renewed pressure from US President Donald Trump for not doing enough to support the world's largest economy.
There are concerns that renewed attacks by Mr Trump on the Federal Reserve could erode investor confidence on its ability to make independent decisions.
Analyst Oliver Pursche, from financial services company Bruderman, said the global picture was precarious.
"What's happening in Hong Kong, what's happening with Brexit and the trade war, it's all a mess," the chief market strategist said. "Every central bank around the world is trying to prop up economies and every politician around the world is trying to destroy economies."