Eastern European hackers have stolen half a million credit card numbers from Australians and racked up $25 million in fraudulent transactions, federal police have revealed.

Australian Federal Police were unable to provide details of their ongoing investigation, but they confirmed they were working with law enforcement bodies in other countries to tackle the organised hacking ring.

Targets of the breaches were often stores in remote places.

"The Australian Federal Police can confirm it is currently investigating a series of merchants whose individual computer systems have been compromised," a spokeswoman told The Age.

"The compromise is believed to have involved approximately 500,000 credit cards and resulted in more than $25 million in fraudulent transactions."