Diageo's operations within the lucrative South Korean whisky market are facing further threats from ongoing investigations into its practices within the country, the company said today. The company lost its import license in the country yesterday after Korean tax authorities found it has been dealing with unlicensed wholesalers. The group said it is now cooperating with prosecutors on an unrelated issue. The investigations are likely to come as a warning to companies working in foreign markets with local partners to ensure all its practices adhere to regulations, or face strong sanctions on their operations. Losing its Korean import license will already be a major blow to Diageo, with the country estimated to be the world's fourth largest market for the lucrative whisky segment.