Europe's main stock markets dropped 0.7% in opening deals on Monday, as investors worried over the festering global trade war.
London's benchmark FTSE 100 index of major blue-chip firms fell to 7 629.01 points compared with Friday's closing level.
In the eurozone, Frankfurt's DAX 30 reversed to 12 497.48, while the Paris CAC 40 declined to stand at 5 350.96 points.
Asian stocks also dipped after US President Donald Trump threatened fresh tariffs on European cars, and amid reports he is mulling curbs on Chinese investment the US.
The news persuaded many investors to dump equities, which are widely regarded as a risky asset in times of economic uncertainty.
"Markets start the week on a risk-off tone after President Trump threatened to impose tariffs on imported cars from Europe - and he is now planning to curb Chinese investments in 'sensitive' US industries," said Konstantinos Anthis, head of research at trading firm ADS Securities.
He added: "Trump's threats to curb Chinese investments in the US are casting doubts on the prospects of the US economy and investors are starting the week with limited appetite.
"Nevertheless, after a few days in the red global stocks are hoping for a reason to rally."* Sign up to Fin24's top news in your inbox: SUBSCRIBE TO FIN24 NEWSLETTER