SYDNEY, Australia -- Nationwide outages hit a major Australian communications company Wednesday, disrupting phone lines, crashing payment systems and impacting millions of customers.

Optus said it was scrambling to restore its mobile and internet services to more than 10 million customers across Australia.

Company chief executive Kelly Bayer Rosmarin told national broadcaster ABC there was "no indication" the outage was the result of hacking or a cyber attack -- but that engineers were yet to pinpoint the issue.

"Our systems are actually very stable. We provide great coverage to our customers, this is a very rare occurrence," she said.

"And when I have more information about the root cause, I will be the first to let our customers know."

Optus said they identified the outage at around 4:05 am local time.

Widespread issues were still being reported across Australia more than seven hours later.

Dozens of hospitals were unable to receive phone calls, and landline phones on the Optus network could not ring emergency services.

The poisons hotline in the state of New South Wales also said it was impacted.

"Our teams are working to restore services as soon as possible," an Optus company spokesperson said in an earlier statement.

"Optus apologises sincerely to customers."

- Travel chaos -

There was rush hour chaos in the city of Melbourne after a "communications outage" disrupted train services, although it was not clear if this was linked to the Optus network.

Australian Communications Minister Michelle Rowland said the Optus outage had been caused by a "deep fault" in a "fundamental" part of the company's network.

"What we do know is that this is a deep fault. It has occurred deep within the network," she told reporters.

"It has wide ramifications across mobile, fixed, and broadband services for Optus customers.

"Customers are clearly frustrated about it, and Optus should respond to that accordingly."

Ramsay Health Care said on Facebook that phones were down at its 73 private hospitals and day surgery units, while Sydney's Westmead Private Hospital also said its phone lines were down.

Other companies to report issues included health insurer Bupa, airline Virgin Australia and health and safety watchdog WorkSafe.

A carer said he had not been able to call an ambulance for one of his patients, telling ABC Radio Melbourne: "I had to run out on the street and borrow a phone from someone walking his dog."

The outages come just over a year since more than nine million Optus customers had their personal data stolen during a cyber attack.