On Sunday, the US Federal Reserve cut interest rates to almost zero and launched a $700bn stimulus programme.
It was part of co-ordinated action announced alongside the eurozone, the UK, Japan, Canada, and Switzerland.
However, investors are worried that central banks now have few options left to combat the impact of the pandemic.
The new governor of the Bank of England, Andrew Bailey, has pledged to take "prompt action again" when necessary to stop the damage to the economy from the coronavirus pandemic.
David Madden, a market analyst at CMC Markets, said that while central bankers were trying to calm the markets, "in reality it is having the opposite effect".