Staff at one of the affected stores at Sydney's Town Hall confirmed the outage meant customers were left with no choice but leave without purchases.
Stores temporarily closed in response to the outage.
"Registers are offline so customers are standing in queues with baskets of food that they can't buy", she said.
A woman named Rose, from Hoppers Crossing in Melbourne, told 3AW customers were offered lollies as they were asked to leave.
More than 20 shoppers were reportedly turned away by the security guard.
Arab leaders gather to unify ranks in face of conflict, wars
The summit also issued the "Dhahran Declaration" which brought the viewpoint of the Arab leaders on the issues related to the region.
Margaret River Pro surf event suspended due to nearby shark attack
Hawaiian pro surfer John John Florence had a close encounter while surfing in the region in the lead up to the competition. Opposition Leader Mike Nahan said the attack would make global news given the Margaret River Pro event was on nearby.
Prime Minister, premiers meet over controversial Trans Mountain pipeline
Superior court which could have the effect of quashing or cancelling approvals that have already been granted" she said. Kinder Morgan, for its part, would not say Sunday whether it felt mollified by the day's events.
According to multiple reports, Woolworths supermarkets around Australia are experiencing a technical issue that prevents them from processing any transactions. The registers are now back online in all our stores.
Seven News in Adelaide is reporting that some customers at a Woolworths store in Adelaide's west got their groceries for free after the nationwide outage.
INITIAL: MAYHEM has erupted at Woolworths stores across the Mackay region as a national technical outage shuts down stores.
The supermarket giant has not yet revealed the cause of the outage.