The European Central Bank warned that "the potential for an abrupt reversal remains significant" on financial markets in its twice-yearly Financial Stability Review.
The warning came on a quiet day with US markets closed for the Thanksgiving holiday. On Wednesday both the Dow Jones Industrial Average and the Standard & Poor's 500 Index closed at record highs.
Trading will resume in New York on Friday though many market participants are expected to remain on the sidelines until next week.
Europe's Stoxx 600 Index finished the day with a 0.2 per cent advance from the previous close. The UK's FTSE 100 Index rose 0.2 per cent, Germany's DAX Index gained 0.3 per cent, while France's CAC 40 Index also added 0.3 per cent.
Elsewhere, the US dollar touched the highest level in fourteen years before giving up some its gains. Zinc and copper advanced in London trade.
"More volatility in the near future is likely and the potential for an abrupt reversal remains significant amid heightened political uncertainty around the globe and underlying emerging market vulnerabilities," the ECB said in its twice-yearly review.