Bankwest services including ATM and EFTPOS transactions, Internet banking and the bank's mobile app and website have been affected by what the bank described as a "connectivity issue".
The bank said that contactless card payments were affected, but inserting a credit or debit card "should" allow payments to be made.
The bank also told its customers that they would have to visit a Bankwest branch to withdraw money while the issue was being addressed.
The bank's website has been redirected to a maintenance message that states the bank is "currently experiencing technical issues".
The bank first acknowledged the issue at approximately 11.50am.
Last week a number of financial institutions including ME Bank and NAB were hit by a major Telstra outage that affected the telco's enterprise services in Victoria for an extended period.
Source: Computerworld Australia
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