'Significant': telco giant Optus probing fresh outage

The embattled telco says it is investigating the issue, which is affecting triple zero calls.

"Optus customers will only be able to call Emergency Services if they are within coverage of another mobile network or are able to call via WiFi," the company's website said.

The failure is the fourth time in months that a major Optus outage has prevented people accessing emergency services. 

A scheduled firewall upgrade in South Australia triggered a communications outage on September 18 linked to the deaths of three Australians. 

Optus chief executive Stephen Rue blamed human error for that fault.

Normal calls were largely unaffected, but the outage blocked about 600 triple zero calls from connecting to emergency services.