The company operating Centra, Mace and Supervalu stores in Ireland has said it has been hit by a cyber-attack.
The County Cork-based Musgrave group confirmed on Tuesday that hackers tried to steal credit and debit card numbers and expiry dates.
It said that its network across the island of Ireland had been affected.
The company said it had detected “malicious software” but there is “no evidence that data has been stolen”.
It added that the software had attempted to take debit and credit card numbers and expiry dates but not cardholder names, PINs or CCV numbers.
Musgrave operates 106 Mace shops, 81 Centra outlets and 36 Supervalu stores in Northern Ireland.
A spokesman for Musgrave added that the firm is “is advising any concerned shoppers to review activity on their statements as a precautionary measure”.
“The company is now engaged in an ongoing investigation and we are in the process of contacting the relevant authorities,” he said.
“Musgrave’s cyber breach response experts have installed advanced technical fixes and continue to actively manage and monitor the situation.”
The Garda Síochána, the Irish police force, confirmed that its cyber crime bureau is investigating the attack and an inquiry is an “an early stage”.