The U.K.'s FTSE 100 underperformed, closing unofficially down 0.5 percent, although a new poll on Wednesday evening showed support for independence had stalled slightly. The results, published in the Daily Record, gave the "no" side a six point-lead.
Heavily-weighted stocks of Lloyds Bank and RBS bucked the trend to closed around 1.1 percent higher after the banks said they would relocate from Scotland to England in the event of independence.
Across Europe, cyclical stocks like automobiles posted the biggest losses. Energy stocks also underperformed, as Brent crude oil fell to a 17-month low below $98 a barrel.
Oil prices also pressured Wall Street stocks downwards. In addition, investors there were concerned by President Barack Obama's announcement of increased airstrikes against Islamic State militants in Iraq and Syria. The U.S. will also provide assistance to opposition forces in Syria.
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Back in Europe, shares of Air France-KLM closed up around 2.6 percent after it unveiled a new strategic plan and pledge to improve core earnings.