Coles supermarkets across the country were unable to open on time on Sunday due to a "network error".

Customers hoping to hit the shops as soon as doors opened were told a nationwide error meant the supermarkets were unable to process sales.

One of the signs spotted outside a closed store read:

We apologise. Our store is currently closed due to circumstances beyond our control. We are working to resolve the issue and will re-open as soon as possible. We apologise for any inconvenience caused.

Another said a "nationwide computer problem" was to blame.

Customers at this Canberra store were only able to pay for groceries through one checkout. ( ABC News: Anna Henderson )

Just after 10:00am, a Coles spokeswoman said all its supermarkets were open and trading.

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"Earlier this morning we had some minor IT problems in some of our supermarkets which were out of our team members' control," the spokeswoman said.

"We apologise for any inconvenience our customers experienced earlier this morning."

Earlier the spokeswoman said the issue may not be impacting all stores but was not able to give a figure of how many were hit.

At one supermarket in Canberra, customers were allowed to shop but could only be served at one register.

Back in April, Woolworths supermarkets were hit by a late afternoon technical glitch, forcing customers to abandon their shopping in the aisles.

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