US stocks had already attempted a comeback on Tuesday from the previous day's heavy losses, but late jitters undermined the recovery.

Dealers said, however, there was no guarantee the rebound in European stocks would last, given deep uncertainty over the conditions of Britain exiting the European Union, and a damaging standoff between Italy and the EU over Rome's budget.

A slowdown in powerhouse Germany's economy is also a worry, they said, after it shrank 0.2 percent in the third quarter, in news which sent the euro sliding against the dollar.

The pound was under pressure as Prime Minister Theresa May defended her divorce deal with the EU before rowdy lawmakers before trying to win the backing of her splintered cabinet.

"Uncertainty around Italy and Brexit are weighing on sentiment," noted CMC Markets analyst David Madden.