In a statement, Ticketmaster said less than 5 per cent of its global customer base had been affected, including Australians, but not customers in North America.
It added: "As a result of Inbenta's product running on Ticketmaster International websites, some of our customers' personal or payment information may have been accessed by an unknown third party."
No confirmed cases in Australia: spokesperson
A spokesperson for Ticketmaster Australia told SBS News there are no confirmed cases of data breaches affecting Australians at this stage.
As a precaution, the organisation has sent emails to customers in Australia and New Zealand who made purchases between September 2017 and February 2018.
"Forensic teams are assessing the issue – but we would like to reiterate there are currently no confirmed cases outside the UK," the spokesperson said.
Australian customers have also been warned to monitor their accounts for signs of fraud or identity theft.
"Forensic teams and security experts are working around the clock to understand how the data was compromised," Ticketmaster Australia said in a statement posted on a website set up to answer queries by Australian customers.
UK customers who had transactions between February and June this year have been issued alerts.
International customers who had transactions between September 2017 and June 23 2018 are being warned they could possibly be affected.
A spokesman for the National Cyber Security Centre (NCSC) in the UK said: "We are aware of a cyber incident affecting Ticketmaster.
"The NCSC is working with our partners to better understand the incident."
- with AAP