Australian officials have promised telecommunications giant, Optus, will face "significant consequences" over a systems outage linked to multiple deaths.

The incident last week left hundreds of people across more than half of the country unable to call emergency services for 13 hours.

Optus - one of the country's two major providers - says at least three people died as a result, and its chief executive has apologised to their families and the public for the "completely unacceptable" failure.

The company is under fire for its delayed handling of the incident - the second such outage for the firm in two years - and the nation's communications regulator is investigating.

More than 600 calls to emergency services failed last Thursday, primarily coming from South Australia, Western Australia and the Northern Territory. At least two calls to triple-0 made from south-western New South Wales also did not connect.

However Optus waited 40 hours to inform the public about the incident, and also did not tell regulators until the issue was resolved - counter to standard practice, the Australian Communications and Media Authority (Acma) says.

In a press conference on Friday afternoon, Optus boss Stephen Rue blamed the outage on a technical fault identified during a network upgrade.

He said welfare checks conducted after services were restored confirmed three people had died, including a baby boy, though police have since said the network failure was "unlikely" to be a cause in that case. Authorities in WA also say they believe a fourth person died after their call to triple-0 failed.

In a series of updates over the weekend, Mr. Rue said the company was unaware of the incident for 13 hours. Multiple customers had tried to advise the company its network wasn't working, but the complaints weren't escalated or handled "as would be expected", he said.

"I would like to reiterate how sorry I am about the very sad loss of the lives of four people who could not reach emergency services in their time of need," Mr. Rue said on Sunday.

"What I can assure you is that actions are and will be taken to ensure this does not happen in future."

In a statement, an Acma spokesperson said the regulator was "deeply concerned" by the situation and its handling.

"Australians must be able to contact emergency services whenever they need help. This is the most fundamental responsibility every telco provider has to the public."

The regulator has previously found Optus failed to provide access to emergency call services for 2,145 people during an outage in 2023, and then failed to check on 369 people affected afterwards. It was hit with more than A$12m ($8m; £6m) in penalties.

Communications Minister Anika Wells on Monday said telecommunications providers had "no excuse" for triple-0 call failures and that she had spoken to Mr. Rue - who the prime minister says should considering resigning.

"You would be unsurprised to hear that I expressed my unbelievable disappointment that we were here again so quickly. Or here again at all."

The company had "perpetuated an enormous failure on the Australian people" and would face "significant consequences", she said.

Investigations are still underway, but Mr. Rue has said he intends to give public updates daily "as more information becomes known." (BBC)