Getty ImagesStock markets in London, Paris and Berlin fell as trading began on Thursday after US President Donald Trump's sweeping announcements on tariffs.
The UK's FTSE 100 share index was down 1% while France's Cac 40 fell 1.7%.
Earlier Asian markets had slid, while the price of gold, which is seen as a safer assest in times of turbulance, climbed to a record high.
Traders are concerned about the global economic impact of Trump's tariffs, which they fear could stoke inflation and stall growth.
Markets across Asia had fallen sharply after Trump's announcement, with the Nikkei in Japan closing down nearly 3% and Hong Kong's Hang Seng index 1.5% lower.
The price of gold hit a record high of $3,167.57 an ounce at one point on Thursday, before falling back.
A combination of a 10% baseline levy and higher duties on a number of other trading partners reverses decades of liberalisation that shaped the global trade order.
"This is the worst-case scenario," said Jay Hatfield, chief executive at Infrastructure Capital Advisors.
"Enough to potentially send the US into a recession," he added, echoing nervous market sentiment.
George Saravelos, head of FX at Deutsche Bank Research, said the new US trade tariffs were a "highly mechanical" reaction to trade deficits, rather than the "sophisticated assessment" the White House had promised.
He warned the move "risks lowering the policy credibility of the [Trump] administration".
"The market may question the extent to which a sufficiently structured planning process for major economic decisions is taking place. After all, this is the biggest trade policy shift from the US in a century," he said.
