Canberra, Millions of Australians were left without a phone or internet connection on Wednesday after Optus, the countrys second-largest telecommunications provider, experienced an unexplained nationwide outage.

The outage crippled payment systems and online operations and led to morning peak-hour chaos as train networks and ride share services were down briefly in some cities.

Optus CEO Kelly Bayer Rosmarin ruled out a cyber attack but in an interview on ABC Radio did not give a reason for the outage, already in its sixth hour, or say how long it would take for services to be restored.

The Australian government said that the network outage at Optus was because of a “deep fault” within the companys networks.

“This is a deep fault, it has occurred deep within the network. It has wide ramifications across mobile, fixed, and broadband services,” federal Communications Minister Michelle Rowland told reporters.

However, Optus, the Australian unit of telecoms firm Singapore Telecommunications, has not yet identified the cause of the outage or how long it would take to restore service.

Source: Qatar News Agency