Telstra has blamed an issue with a time-keeping server for a major outage in which thousands of mobile customers were unable to make calls or access data on the country’s largest network on Wednesday morning.

The telco, which powers about 25m mobile services nationwide, confirmed the outage on Wednesday, with 90% of services restored after 10am AEST.

Telstra’s chief financial officer, Michael Ackland, who has been acting chief executive while Vicki Brady is on leave, said the outage began at 4.30am AEST, and was an intermittent issue affecting calls and data services.

He said there was no indication it was the result of malicious activity, but the company did not know exactly what caused the issue.

“The issue is impacting a number of nodes within our network that keep time across the mobile network,” Ackland told reporters.

“And when these nodes are not operating as expected, which is what has occurred, other parts of the network can be affected, resulting in intermittent issues with some mobile calls and data sessions.”

He said the company acknowledged the outage “has been a big disruption to many people’s days. And we apologise for that.”

More than 7,500 customers reported the network disturbance on online monitoring platform Downdetector.

All of Victoria’s regional train services have been suspended as a result of radio network issues, which the operator said were caused by the Telstra outage.

Transport Victoria said V/Line services were “unable to operate” on Wednesday morning, with no estimated time for rectification.

Some regional commuters in New South Wales were also facing disruptions after two train routes went down due to an “external telecommunication issue”, which the operator confirmed was the Telstra outage.

Transport NSW said trains were not running between Campbelltown and Moss Vale/Goulburn on the Southern Highlands line, and there were no trains running between Newcastle interchange and Maitland.

Replacement buses were being organised.

Telstra operates the triple-zero emergency call system, but it remained available for non-Telstra customers during the outage.

Ackland said the company was conducting welfare checks on customers who attempted to dial triple zero during the outage but did not have any information as of Wednesday morning.

“We don’t believe this issue has impacted triple zero in the same way as other calls,” he said.

“It uses different network settings, but we are continuing to investigate every, every angle on … where it may have impacted triple zero if that has occurred.”

In a statement, the communications minister, Anika Wells, and the emergency management minister, Kirsty McBain, said the Triple Zero Custodian has reported that some emergency calls did not connect.

“The core triple-zero system remains operational, with connected calls flowing as expected from carrier networks to the Emergency Call Person (ECP), and on to state and territory emergency services dispatchers,” Wells and McBain said.

“However, the Triple Zero Custodian has advised that some callers were unable to connect to the ECP, and that these are being investigated by Telstra.”

They said the Australian Communications and Media Authority will conduct an investigation into the outages.

WA police said the Telstra outage was affecting calls to triple zero and advised people to offer support to vulnerable family members.

Eftpos systems were also taken offline during the outage, affecting taxi payments in NSW and in retail environments, according to providers CommBank and Tyro.

Time-keeping nodes being restored

Telstra said it was in the process of restoring the affected nodes, although Ackland said it would take time to reset across the network.

Customers still having trouble making a call were encouraged to try again, as it may work on the second attempt.

The affected Telstra datacentres are based in Sydney and Melbourne.

“Lots of computer systems, they have to synchronise time. It’s one of the ways that you authenticate what’s going on in the network and the time synchronisation in those nodes, wasn’t wasn’t working as it should,” Ackland said

“We don’t know why yet.”

The prime minister, Anthony Albanese, said the outage was “deeply concerning”.

“It’s very disruptive to people’s lives throughout the country,” he said.

“Some people have been unaffected, but many have been severely disrupted. Telstra are investigating but we’re working closely with them.”

The opposition leader, Angus Taylor, demanded the government “front up” and explain the outage to Australians.

Taylor called on Wells to provide an explanation.

“The government needs to explain what has gone on here, why has this happened, what they’re going to do to make sure it’s fixed and never happens again,” Taylor said.

The Telstra outage comes after other telecommunications giants Vodafone and Optus experienced problems.

In June, Vodafone customers were left with intermittent reception and data issues across Australia.

Two deaths have been linked to an outage at Optus in September 2025, which lasted almost 14 hours and affected hundreds of calls in four states and territories.

New rules were handed down by the Australian Communications and Media Authority in March requiring telcos to publish when an outage started and when it was restored in detail, as well as the cause.