Radisson Hotel Group has confirmed that its reward system database has suffered a breach with members' names and addresses among the information compromised.
Impacted Radisson Rewards members were notified by the company after the breach was discovered on 1 October.
In a statement Radisson said: "The data security incident impacted less than 10% of Radisson Rewards member accounts and did not compromise any credit card or password information. Our ongoing investigation has determined that the information accessed was restricted to member name, address (including country of residence), email address, and in some cases, company name, phone number, Radisson Rewards member number and any frequent flyer numbers on file."
The group has said that all impacted member accounts have been secured and are being monitored for any suspicious activity.
The company added: "We take the data privacy and security of our members very seriously and are conducting an extensive ongoing investigation into the incident to help prevent data privacy incidents from happening again in the future."