In a volatile session which saw the STOXX 600 seesaw in and out of positive and negative territory, the pan-European benchmark ended 0.6 percent lower.

Fresh losses in emerging markets and worries Washington will follow through on plans to levy an extra $200 billion of Chinese imports kept investors on edge.

"The turmoil within emerging markets also continues, widening from Argentina and Turkey, (is) dampening global sentiment even further all the while we await the US decision on additional China import tariffs," Accendo Markets analyst Mike van Dulken said.

A consultation period on the proposal to slap fresh tariffs on China ends on Thursday, paving the way for a decision, although it is unclear how quickly that will happen.

Commodity-related sectors such as oil & gas and basic resources were among the biggest fallers.

"Dealers are not showing any major appetite for relatively risky assets like stocks," David Madden, market analyst at CMC Markets UK, said.

Tech stocks were also notable fallers, dropping 1.2 percent to their lowest level since early May.

Earlier in the session, Apple suppliers Dialog Semiconductor and AMS all came under pressure, with traders citing disappointing August sales unveiled by Taiwanese peer Largan Precision.

The losses accelerated towards the end of the session after US peer Micron's shares tumbled on the back of its CFO's comments about chip pricing.

Utilities were the strongest gainers, however, with Italy's state-controlled Enel rising 2.1 percent after Goldman Sachs upgraded the stock to buy. Analysts at the US bank said Enel has the capacity to buy back 10 billion euro worth of shares over the coming years.

In Britain, Centrica added 5 percent after the local regulator set an energy price cap that was at the lower range of analysts' expectations.

The top individual gainer on the STOXX was Safran, which rose to a fresh record high after a strong update.

The world's No. 3 aerospace supplier raised full-year forecasts following better-than-expected results in the first half on strong demand for spares and services.

Safran gained 6.4 percent, supporting other aerospace stocks including plane maker Airbus, which rose 1.2 percent.

Weir Group was the biggest faller, down 8.6 percent after the maker of pipes for the energy and mining industries said there were initial signs of pricing pressure and flagged a softening in demand.