The US Federal Reserve and European Central Bank said tonight they are open and operating will provide liquidity to financial markets as needed.
Fed spokesman Mr David Skidmore read a short statement on a conference call with reporters. He gave no further details.
In Basel, Switzerland, New York Fed President William McDonough told Reuters that the US central bank is coping with the situation.
US financial markets were closed but news of the incident wiped 288 points, or 5.7 per cent, off the value of London's FTSE 100 index. The fall was the largest one-day point loss since October 1987 and erased £67 billion from the index's value.