Australian telecoms giant Optus has repeatedly apologised for Wednesday's communications outage, though not yet offered a full explanation of the root cause

Sydney (AFP) - Australia’s government on Thursday launched an investigation into a nationwide communications outage that crippled phone lines and severed internet access for 10 million customers.

For almost 12 hours Wednesday, the unexplained glitch crashed electronic payments, disrupted phone lines used by emergency services and stopped people accessing government systems.

Telecommunications company Optus – Australia’s second-largest phone provider with more than 10 million customers – has repeatedly apologised for what it described as a “technical network outage” but did not offer a fuller explanation of the root cause.

Communications Minister Michelle Rowland said a government review would now focus on understanding how the “particularly concerning” network failure occurred.

“It is critical that industry and governments take stock following large-scale outages, given no network is immune,” she said in a statement.

Optus and the government are at odds over the company’s handling of the crisis and whether impacted businesses should be paid out after effectively losing a full day’s trading.

While Optus executives have shut down talk of compensation, Rowland said it was “reasonable” for aggrieved customers to expect some form of redress.

Rowland said a separate investigation, conducted by the government’s communications regulator, would assess whether Optus had failed its obligations to carry phone calls made to emergency services.

According to polling company Roy Morgan, Optus was already one of Australia’s least-trusted brands.

Just over one year ago, more than nine million Optus customers had their personal data stolen in a cyber attack.

Chief executive Kelly Bayer Rosmarin said the company would “work even harder to retain our customers’ trust” in a statement released Thursday alongside the company’s half-yearly earnings.

A host of organisations and businesses were hit by the outage, including the federal department of education, the Royal Melbourne Hospital, and Australia’s Commonwealth Bank.

Landline phones on the Optus network were unable to ring emergency services, and thousands of commuters were stranded when rush hour trains were briefly halted.