A technical glitch caused hundreds of triple zero calls through Optus to fail in three Australian states, including in households where people died.

Up to 600 households in South Australia, Western Australia and the Northern Territory were impacted by the triple zero outage during a network upgrade on Thursday, Optus chief executive Stephen Rue said.

"I have been advised that in the process of conducting welfare checks three of the triple zero calls involved households where a person tragically passed away," Mr Rue told reporters in Sydney on Friday.

"Please know that these welfare checks are ongoing."

He said the technical problem on the network had been resolved.

The boss of Australia's second largest telco provider offered "a sincere apology to all customers who could not connect t

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