The European Central Bank (ECB) left interest rates unchanged on Thursday, as expected following last month's unexpected cuts. Instead, ECB President Mario Draghi gave more details of the bank's asset-purchase plan, devised to boost the euro zone's struggling economy.

Markets had been expecting more details on the total volume of the program and country distribution, however, along with some hints about a Federal-Reserve style quantitative easing (QE) program. Draghi's failure to address these issues sent European bourses lower.