Nationwide customers were unable to access online or mobile banking services this morning due to an unspecified 'IT issue'.

Customers took to Twitter on Thursday morning to complain that they were unable to access account information online or through Nationwide's banking app.

Charlotte Davies (@Charlalar) said: "Finally got paid today but have no idea how much because the @Nationwide website is down AGAIN. For crying out loud!"

Another customer, David Goodwin (@TheGingerDog) commented: "Hmm. My bank accounts have all disappeared and now I've been locked out. Not a good start to the day @asknationwide #nationwide #fail."

Nationwide subsequently responded to complaints on its @AskNationwide account, apologising to those affected by the outage: "Some customers were unable to access accounts this AM due to a technical fault. This has been fixed & we apologise for any inconvenience."

A spokesperson confirmed to ComputerworldUK that the outage lasted approximately two hours from around 7.30am, resulting in online and mobile banking customers being unable to access any account information. Branches, ATMs and other services were not affected, and a full service has now been resumed.

However the spokesperson declined to explain the nature of the outage, only indicating that it was related to its underlying IT systems.

It is the second outage that has affected Nationwide's online and mobile banking customers in recent months, with an outage in April lasting most of the day.

Nationwide overhauled its ageing online banking systems in 2011 to help improve usability, in a project led by IBM. The building society's core banking systems running on SAP software, put in place as part of a £300 million systems overhaul.