European stocks reversed early gains on Wednesday and lost ground, hit by renewed worries over the euro zone debt crisis ahead of an Italian debt auction, and after Iran's threat to stop the flow of oil through the Strait of Hormuz.

At 8:34 a.m. (British time), the FTSEurofirst 300 <.FTEU3> index of top European shares was down 0.4 percent at 986.11 points, led by miners and banks.

(Reporting by Blaise Robinson)