Optus could face multi-million dollar fines and legal penalties after a botched network upgrade prevented people from making triple-zero calls and resulted in three deaths, including of an eight-week-old boy.

The telco has admitted up to 600 households in South Australia, Western Australia and the Northern Territory were impacted by the triple-zero outage on Thursday.

SA police said an eight-week-old boy from the town of Gawler and a 68-year-old woman from the Queenstown suburb of Adelaide died.

At least three customers, two in South Australia and one in Western Australia, died after they were unable to call emergency services, Optus chief executive Stephen Rue confirmed.

Communications Minister Anika Wells said the incident was "incredibly serious and completely unacceptable".

"The i

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