Luxury hotel chain Mandarin Oriental has launched an investigation after hackers stole credit card data on its company network.
In a statement, the group confirmed the data went missing from card processing systems at some of its US and European hotels.
It warned other hotel groups to be on their guard and also advised its guests to keep an eye on their credit and debit card statements.
The group said it believed only credit card numbers had been stolen, not other security codes used in conjunction with payment, nor any personal details.
It did not specify how many hotels have been hit or the amount of data that has gone missing.
"While the group has leading data security systems in place, this malware is undetectable by all anti-viral systems," said the statement.
"We take the protection of customer information very seriously. Unfortunately incidents of this nature are increasingly becoming an industry-wide concern and we have therefore also alerted our technology peers in the hospitality industry."
The group said it acted quickly to address the issue, working with forensic experts to remove the malware.
"Guests can be confident that security protocols are being thoroughly tested at all hotels to protect guest information and prevent a recurrence of such an attack.
"While we have executed additional security protocols, we do not wish to disclose specific details of our security measures."
