Millions of customers impacted as online banking outage hits ...

Millions of Westpac and St George customers were locked out of their online banking for about two hours today due to an outage.

The bank confirmed some customers were unable to access the Westpac app due to an unexpected issue.

Westpac's online and banking services have since been restored nearly two hours after it was first reported.

"We apologise for the disruption this afternoon and thank you for your patience during this time," Westpac said in a statement.

The outage occurred about 1.40pm and impacted customers at Westpac, St George and Bank SA.

"We're aware that some customers are currently experiencing intermittent issues with Online Banking," Westpac said in a statement.

"We're working to fix the issue as a priority and apologise for the inconvenience."

St George, which is part of Westpac Group, also confirmed it was experiencing outages.

Some customers on social media noted they could not log onto the app or online banking via desktop.