Woolworth

Many of those shops are former Woolworths or Wilko branches, which it hoovered up after the two brands collapsed.

Coles said it would defend itself against the allegations, while Woolworths said it would review the claims.

Payment systems went down at Australian stores including Woolworths, while financial institutions such as the National Australia Bank were also affected.

Medhi Mammadov's co-workers asked each other as their office on the 27th floor of the iconic Woolworth Building began to shake.

Woolworths - the nation's largest retailer - and its rival Coles control 65% of the market, and both have been facing intense criticism over their business models as the country battles a cost-of-living crisis.