Westpac (ASX: WBC) has now assured there had been no compromise of its security or systems.

In a statement, Westpac said it “would like to confirm that there has been no compromise of its banking systems following reports of a credit card merchant security breach.”

“The bank has blocked a number of cards which it has determined have been, or are at risk of being affected.

Westpac said none of its customers will be liable for any confirmed fraudulent transactions experienced as a result of this situation.

“Westpac encourages all customers who have any concerns about transactions which may appear on their account to contact the telephone number which can be found on the back of their credit card,” the bank said.

This latest glitch in Australia's banking systems reportedly affected CBA, St George and NAB, all of which have either blocked or cancelled credit cards as a cautionary measure.

Commonwealth Bank said in a statement this morning, it had informed 8000 customers of the potential breach involving the credit card facilities of a local merchant.