MILAN (Reuters) - Shares in Italy's two biggest banks, UniCredit (>> UniCredit SpA) and Intesa SanPaolo (>> Intesa Sanpaolo SpA), tumbled more than 20 percent at the open on Friday after Britain voted to leave the European Union.

UniCredit hit an all-time low of 2.052 euros, down almost 25 percent. Both UniCredit and Intesa shares were later suspended temporarily from trade.

(Reporting by Silvia Aloisi; Editing by Mark Bendeich)