European stock markets trimmed last week's gains to close lower on Monday, off the back of weak Chinese data and heightening tension in Ukraine.
The pan-European FTSEurofirst 300 index provisionally closed down 1.1 percent at 1,293.10 points, with Russia's Micex index also turning lower by 0.7 percent as relations between the West and the Kremlin looked set to dominate markets this week once more.
On Monday, reports by Reuters suggested that Russian troops had forced their way into a Ukrainian marine base in the Crimean city of Feodosia early during the day. According to reports, Russians used stun grenades and fired automatic weapons as they charged in.
U.S. President Barack Obama arrived in the Netherlands on Monday for talks with the G-7 countries, during which he sought support from European allies and China to economically isolate Russia.
Concerns over China also took center stage on Monday, with manufacturing PMI showing activity continued to decline in March for a fifth month in a row. It hit a new eight-month low of 48.1, compared to 48.5 in February.
Meanwhile, U.S. stocks also fell on Monday, with Wall Street retreating after last week's gains, with the Nasdaq Composite particularly hard hit as investors sold some of its recent high flyers.
In addition, a reading on U.S. manufacturing slipped in March, with factory activity slowing to 55 from a near four-month-high of 57.1 in February. Readings above 50 signal expansion.
Back in Europe, the German DAX provisionally closed lower by 1.7 percent, following data that showed growth in business activity in the country slowed in March. German business activity fell from the 33- month high reached in February to 55.0 in March.
However, France's private sector enjoyed its fastest growth rate in more than two and a half years. The composite output index rose to 51.6, up from 47.9 in February, according to Markit, marking the sharpest rate of expansion in 31 months.
(Read more: France on the mend as German firms take a breather)
After Britain's National Institute for Health and Care Excellence told the U.K.'s National Health Service that it should not use Bayer's new prostate cancer drug Xofigo, shares of the company closed lower by around 3.3 percent. Other drugmakers also saw declines, with GlaxoSmithKline and Sanofi down by 1.0 percent and 1.2 percent respectively.
BNP Paribas bank announced on Monday that it was going to cut 1,600 staff in Ukraine by 2015 as part of restructuring in the face of a tough economic environment. Shares closed lower by 1.8 percent.
Going against the continent's trend downwards, shares in Deutsche Post rose 1.7 percent after Chief Executive Frank Appel revealed a new profit target of 1.6 billion euros ($2.21 billion).