Global markets fell after weak Chinese data and worries that the US Federal
Reserve may slow its monetary stimulus.
In Asia, the fall was led by Japan's Nikkei index, which closed down 7.3%,
having fallen as much as 10%.
European markets also reversed recent rises, with London, Frankfurt and Paris
opening almost 2% lower.
It followed data showing a slowdown in Chinese manufacturing, and Fed chairman
Ben Bernanke's hint that Quantitative Easing efforts may be scaled back.
Also, activity in the eurozone's services sector continued to contract in May,
closely-watched preliminary data from Markit, a financial information services
company, showed.
In Asia, Hong Kong's Hang Seng dropped 2.5%, and South Korea's Kospi lost 1.2%.
Markets in Australia and Singapore also fell.
The China data showed that factory activity contracted for the first time in
seventh months in May.
The preliminary HSBC Purchasing Managers' Index (PMI) for May fell to 49.6. A
figure below 50 indicates a contraction.
Analysts said the figures suggest that the Chinese government's target of
achieving 7.5% growth this year may be missed.
"It's no secret. The true picture is that China's export sector is slowing
down, and its manufacturing sector is also slowing down. That means the trade
surplus is almost gone," said Francis Lun, chief economist at GE Oriental
Financial Group.
'Overheated'
In April, the PMI had fallen to 50.6 from 50.9 in March, underlining that the
economy's pace of expansion was slowing down.
Investor sentiment had already soured on Wednesday after Mr Bernanke told a
congressional committee that the central bank could scale back the pace of bond
purchases later this year.
"Fed chairman Ben Bernanke's much anticipated testimony... certainly initiated
the volatility" on stock markets, said Spreadex trader Max Cohen.
The bond purchases, known as Quantitative Easing, are designed to pump
liquidity into the financial system to bring down borrowing rates for
households and businesses, therefore shoring up the economy.
But some Fed officials have recently warned that continuing the asset purchases
could lead to a spike in inflation.
Neil MacKinnon, economist at VTB Capital, said that while the financial markets
were focused on Mr Bernanke's testimony, in his view "it says more about an
equity market that is 'overheated' and due a correction rather than any
suggestion from the Fed that monetary stimulus is about to be withdrawn".