European stock markets trimmed gains in afternoon trade on Monday after the U.S. said it has taken further action against Russia, imposing sanctions on seven high-profile individuals and 17 companies. The White House said the sanctions are a response to Russia's "continued illegal intervention in Ukraine." The Stoxx Europe 600 index was up 0.1% at 333.76, after trading as high as 335.59 ahead of the U.S. action. Russia's blue-chip MICEX index fell 0.1% to 1,279.08. The U.K.'s FTSE 100 index gained 0.1% to 6,690.67, while France's CAC 40 index rose 0.1% to 4,446.00. Germany's DAX 30 index traded 0.2% higher at 9,423.14.