Victim of Credit Card Fraud (For Settlement)

My family went for vacation on August 15-22, 2014 in Athens, Greece. Everything seemed to be perfect until my husband told that he was missing his bag that contained all the travel documents, money and credit cards. All but 3 cards were used by the thieves to withdraw money through cash advance from Citibank, Greece. Mastercard and the banks lost few minutes to close it, and thus the transactions went through amounting to almost 15,000 Euros. WE ARE VICTIMS OF CREDIT CARD FRAUD. We are perhaps required to pay this amount plus interest if our dispute will not be succesful. Thank you in advance.