Global stock markets turned negative Monday after about 10 people were killed in an explosion on the Saint Petersburg metro system, with authorities opening a terror probe.
"Early gains slipped away by the afternoon following some disappointing manufacturing data and reports of deadly explosions on the St Petersburg subway," said London Capital Group analyst Jasper Lawler.
After initially opening firmer, Wall Street fell back, dragging the main European markets down with it -- even Frankfurt where positive economic data had earlier pushed the blue-chip DAX 40 index closer towards a new record high.
Traders said investors were keeping cautious ahead of key economic data and a meeting this week between US President Donald Trump and China's Xi Jinping.
But in Europe, Frankfurt's benchmark DAX 30 index had climbed as high as 12,375.58 points on the first trading day of April and the first trading day of the second quarter.
That was a whisker away from its all-time peak of 12,391 that was set on April 10, 2015.
Global equities are making a cautious start to the new quarter," said Accendo Markets analyst Mike van Dulken.
"Big corporate moves are thin on the ground and after a busy prior week geopolitical concerns have cooled. However, event risk looms large in the form of (US Federal Reserve) minutes, the Trump-Xi meeting and the US jobs report on Friday," van Dulken said.
FXTM analyst Lukman Otunuga similarly felt that a "sense of caution lingered across the board ahead of a data-packed week."
There was "moderate appetite for risk" in Europe, but "gains on Wall Street could be limited if market participants decide to observe the action from a safe distance," the expert said.
"Much attention will be directed towards Donald Trump's pending meeting with Chinese President Xi Jinping. Any complications or tension in the meeting could spark risk aversion consequently pressuring stock markets," Otunuga said.
- Falling unemployment -
Among the new economic data in Europe, unemployment in the eurozone fell in February to its lowest level since May 2009 as a hiring spree took hold despite uncertainty over Brexit, EU figures showed.
Among the different movers, energy major BP saw its share price gain 0.91 percent to 461.70 pence in London following news of a major disposal.
BP announced it had struck a deal to sell the Forties pipeline in the North Sea for $250 million (235 million euros) to peer Ineos.
The transaction will see Ineos take control of a system that delivers almost 40 percent of Britain's oil and gas.
The Forties pipeline was opened in 1975 by BP and comprises more than 100 miles of pipes with the capacity to transport 575,000 barrels of oil per day from North Sea and several Norwegian fields.
Shares (Berlin: DI6.BE - news) in Reckitt Benckiser (Xetra: A0M1W6 - news) added 0.3 percent after the British household goods company revealed it was mulling the sale of its French's Foods division, which makes mustard and ketchup.
- Key figures at 1600 GMT -
New York - Dow: DOWN 0.5 percent at 20,533.71 points
London - FTSE 100: DOWN 0.6 percent at 7,282.69 (close)
Frankfurt - DAX 30: DOWN 0.5 percent at 12,257.20 (close)
Paris - CAC 40: DOWN 0.7 percent at 5,085.91 (close)
EURO STOXX 50: DOWN 0.8 percent at 3,472.94 (close)
Tokyo - Nikkei 225: UP 0.4 percent at 18,983.23 (close)
Hong Kong - Hang Seng: UP 0.6 percent at 24,261.48 (close)
Shanghai - Composite: Closed for public holiday
Euro/dollar: DOWN at $1.0659 from $1.0664
Pound/dollar: DOWN at $1.2483 from $1.2502
Dollar/yen: DOWN at 110.94 yen from 111.36 yen
Oil - West Texas Intermediate: DOWN 34 cents at $50.26 per barrel
Oil - Brent North Sea: DOWN 39 cents at $53.14