"We apologise to all affected customers and their customers for the impact that this has caused."

Just some of the other businesses affected by Telstra's latest outage.

More than 60 Myer stores across Australia were cash-only for six hours, as the widespread fallout from the Telstra outage becomes apparent.

The retailer is just one of a host of major Telstra fixed-line customers that were hit by another outage on Thursday, including Officeworks, The Good Guys, Medibank, Monash University, Jetstar, Simply Energy and ME Bank.

Telstra's seventh network outage this year came just 24 hours after chief executive Andy Penn briefed journalists on a $250 million program to improve infrastructure.

Telstra warned on Thursday night it could be some time before the outage was repaired.

A map of social media reports about Telstra's network outages. Credit:aussieoutages.com

Politicians and government services, including hospitals and transport ticketing system myki, have all been affected.

The Royal District Nursing Service, which operates nationwide, said the outage disrupted appointments with some home-nursing visits not occurring.

Telstra was hit by another outage on the last day of the financial year. Credit:Craig Sillitoe

"This has affected our visits to many of our clients' homes, many of whom are elderly," spokesman John Allin said.

"We sincerely apologise for delayed or missed visits but we are confident that our scheduling will return to normal as soon as the Telstra issue's rectified."

Hospitals including the Royal Melbourne Hospital (its webmail system went down), Malvern Cabrini and Mitcham Private Hospital in Melbourne reported being impacted.

Melbourne man, Dave Glover, tweeted that he had his hospital procedure cancelled because of the outage.

He told Fairfax Media he had a difficult biopsy scheduled but Malvern Cabrini could not proceed because digital images were held on an offsite server that could not be accessed.

Outage reports have been centred mostly in Victoria and NSW, including Melbourne's CBD.

A Telstra spokesman said it was aware "an issue impacting some business and enterprise customers in Victoria".

"We are investigating the cause and working to restore services as soon as possible," he added.

Political electorate offices, two days out from the federal election, have been ground to a halt.

All political parties were impacted because their internet is provided by the Department of Finance, though phone lines are still working.

The department's IT helpline answered with a recording: "There is currently an electorate office network outage that is being investigated".

The outage also affected Labor's Melbourne-based campaign headquarters, which had to fall back onto contingency measures.

A Myer spokeswoman said its 66 stores nationwide operated as usual, but customers had been unable to pay with bank cards from about 1.30pm to 8.30pm.

"Our ... website is fully functioning" she said.

She declined to comment on whether the outage had lost sales because of the problem.

NAB customers have also been affected, with the outage causing problems to its internet banking and at its contact centre.

"We're working with our suppliers to restore services as soon as possible," a spokeswoman said.

"We apologise for any inconvenience caused to our customers."

Some customers have taking to social media to vent their frustration.

"What do you plan to do to fix this issue?!" Chantal King asked Telstra on Facebook.

Corporate and enterprise customers have been hit by this outage, rather than consumers.

Adding to the frustration would be the outage occurring on the last day of the financial year, when many businesses finalise their finances.

Maree Mitchell, was upset at the timing of the outage.

"Seriously, at close of day at end of financial year?" she wrote.

"Are you going to pay the tax for us because of the transactions we couldn't make? Sorry doesn't pay the bills."

Users in NSW and Victoria noticed connections dropping out around 1.40pm on Thursday, according to reports on Twitter.

Jetstar customers at Melbourne airport experienced delays from 2pm until services were restored around 4.30pm.

"The system is now back online and we're working to resume normal operations at Melbourne Airport," a spokesman said.

The airline was checking people in manually during the outage and at least five domestic flights were substantially delayed.

One user on IT discussion forum Whirlpool suggested it was a state-wide IP network outage in Victoria.

Commuters ran into trouble on their way home from work with the myki website also down due to the outage.

A Public Transport Victoria spokesman said myki users were also unable to top up their cards through their call centre.

He said commuters would need to top up their cards at machines, trains stations and retailers.

It was unknown when the site would be up again, he said.

VicRoads also reported disruptions to its call centre, website and payments system.

On Wednesday, Mr Penn revealed Telstra was spending $250 million to improve the networks, but not outside its normal $4 billion capital expenditure program.

The telco giant has been hit by several outages this year on its mobile and fixed network and has had to offer free usage to compensate angry customers.

However, even Telstra has been affected by Thursday's mass outage.

Its advertising subsidiary Sensis, in which Telstra owns a 30 per cent stake, was unable to receive inbound calls.

It advised White Pages and Yellow Pages that customers might not be able to view their online accounts.

A Telstra spokesman said it could be some time before the outage was fixed.

"We have a fault that has overloaded traffic in part of our enterprise IP network in Victoria," he said.

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"We are currently in the process of isolating the impacted points of presence and will be reconnecting them progressively."

With Chloe Booker, Thomas Hounslow, Neelima Choahan and AAP