Commonwealth Bank call centres, branches inundated with calls ...

Commonwealth Bank call centres and branches have been inundated with calls from customers as the bank urgently works to fix an issue that has seen some of its services go down this morning.

Users attempting to log in to online banking may not be able to access their account.

"We are aware some customers are experiencing intermittent difficulties accessing some of our services," CommBank said in an update on its website at midday.

"We are urgently investigating this and we're sorry for any inconveniences caused."

The bank said call centres and branches are experiencing high volumes of customer enquiries at the moment due to the difficulties accessing the services.

"There may be longer than usual wait times," CommBank said.

"We thank customers for their patience and ask our customers to please be mindful of the wellbeing of our people as they continue to serve our customers."

The bank told customers it will provide updates as they become available.

Sign up here to receive our daily newsletters and breaking news alerts, sent straight to your inbox.