A "system issue" left Bankwest customers with limited access to internet banking, ATMs and even over-the-counter services in bank branches on Friday morning.

The outage lasted until around 10.05 AEST, when a message on the bank's Facebook page indicated services had returned to normal.

A notification appeared on the bank's internet services on Thursday night saying the system was down for maintenance and would be back up by 2.30am Perth time. However when customers tried to access their money on Friday morning, the message was still there.

The bank issued a statement early on Friday saying it was aware of "a system issue causing limited access".

"We're working to fix this as our highest priority. We'll provide a further update as soon as possible. All customer funds and data are safe", the statement said.

In an update at 7.13am Perth time (9.13am AEST), the bank said "Bankwest App, online banking, ATMs, and EFTPOS are intermittently unavailable", adding that stores were also experiencing issues.

The error message on the bank's app was also updated at around this time, indicating at least some progress in addressing the problem was being made.

Bankwest customer John Gillespie was unaware of the issue as he headed off to work on Friday morning, but found his card didn't work as he attempted to buy some food. Needing to fill his car with fuel in order to get to work, he called the bank and was told there may be no way to access his money.

"I rung up at 8am to find out what was going on, and they said no-one can access their money. I can't withdraw, I can't go online. It's really put me in a bad spot," said Mr Gillespie, who had to return home.

"There's a lot of people put out, and I'm not that happy myself to be honest," he said. "I can't afford days off work."

Similar stories emerged on Twitter, as the official Bankwest account fielded queries from upset customers who could't get to their funds.

In an update at 8.45am Perth time, or 10.30am AEST, the bank said ATM and EFTPOS transactions were being restored, although "customers may experience some interruptions as these services come back online". Mobile and internet banking services were still experiences issues, the update said.

Shortly after 8am Perth time, 10am AEST, full service appeared to be restored.