The bank says the measures are temporary and aimed at protecting customers
Bank of Ireland has heavily restricted some debit cards amid concerns the cards have been compromised.
Impacted customers have been temporarily unable to use their cards for online or contactless transactions.
The cards can still be used at ATMs or in chip and pin devices.
It is not clear exactly how many customers have been impacted, with the Irish Times reporting the number 'appears to be significant'.
Those who have been affected have received messages about the issue, and new cards are now being sent to some customers.
In a statement, Bank of Ireland said: "Customers who have received a proactive care message can still use their existing card for chip and pin transactions via ATM or in shop terminal using their confidential four digit pin.
"Online and contactless functionality is temporarily removed from a customer’s card due to the potential for fraud.
"We understand that this is an inconvenience - however it is temporary and implemented in order to protect the customer from fraud."
The bank highlights recent data breaches affecting the likes of Ticketmaster and the Marriott hotel group as a reason for 'heightened precautionary activity' recently.
It also says cards can be compromised when ATMs are 'tampered with'.