Australia's second-largest telecommunications company has apologized after three customers died during a network outage that impacted hundreds of calls to emergency services on Thursday, reported Xinhua.

Optus, a wholly owned subsidiary of Singaporean conglomerate Singtel, on Friday confirmed that a network update on Thursday resulted in the failure of calls to Australia's national emergency telephone number, Triple Zero.

Optus Chief Executive Officer Stephen Rue said at a press conference in Sydney that approximately 600 customers in the states of Western Australia (WA), South Australia (SA), and the Northern Territory (NT) were affected.

"During the process of conducting welfare checks, three of the Triple Zero calls involved households where a person tragically passed away," Rue said.

Two of the deaths were in SA and one was in WA.

He said that the technical failure has been rectified and that Optus would cooperate fully and transparently with all relevant government agencies and regulatory bodies.