Radisson Hotels & Resorts said Wednesday its computer systems have been accessed without authorization, affecting an unknown number of people.
Radisson, which could not be immediately reached for comment, said in a statement it has informed customers of the situation and that guest information may have been accessed, including credit card numbers. Social security numbers were not included.
Radisson did not specify how many hotels or customers were affected but advised that all guests review their account statements and report unauthorized purchases to the bank that issued the credit card, as well as law enforcement authorities.
The computers were accessed between last November and May.
"Working with law enforcement and forensic investigators, we are conducting a thorough review of the potentially affected computer systems and have implemented additional security measures designed to prevent a recurrence of such an attack and to protect guest privacy," said Fredrik Korallus, executive vice president and chief operating officer.
Radisson, which operates more than 400 hotels in 68 countries, is based in Minneapolis.