Optus has been savaged for "reprehensible conduct" after the death of an eight-week old baby during a botched network upgrade that prevented people making triple-zero calls.

South Australian Premier Peter Malinauskas blasted the telco after it admitted up to 600 households in his state, 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.

Mr Malinauskas lashed Optus for leaving his government in the dark about the deaths before holding its own press conference where it announced them.

"I have not witnessed such incompetence from an Australian corporation with respect to communication worse than this," he told repo

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