"Just as you shouldn't breathe too big a sigh of relief after earth tremors end, we remain anxious of a market that seems jittery, even against the backdrop of a very strong U.S. economy," they told clients.

European shares have underperformed their American peers since the beginning of the year and analysts believe companies that fail to meet expectations during the third quarter earnings season will be severely punished.

Shares in the Spanish supermarket chain Dia sank 40 percent after it issued its third profit warning in 12 months and suspended 2019 dividend payments.

A profit warning from the British fashion group Superdry sent its shares down 17 percent.

...