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London's benchmark FTSE 100 index shed 0.6 percent to 7,224.83 points.
In the eurozone, the Paris CAC 40 index dropped 1.1 percent to 5,358.10 points and Frankfurt's DAX 30 slid 0.7 percent to 12,098.02, compared with Wednesday's closing levels.
This week's crucial two-day trade meeting in Washington, which kicks off later Thursday, has taken on huge significance after US President Donald Trump threatened to ramp up tariffs on Chinese goods from Friday blaming backsliding by Beijing.
"The coming hours will be absolutely crucial for markets," said FXTM analyst Han Tan.