Australian government agencies held crisis talks on Sunday in response to a "serious and ongoing" cyber incident that has disrupted operations at key ports across the country.

Port operator DP World halted internet connectivity at its terminals in Sydney, Melbourne, Brisbane and Fremantle on Friday to prevent "any ongoing unauthorised access" to its network, a company spokesperson said.

Home Affairs and Cyber Security Minister Clare O'Neil said Sunday on social media platform X, formerly Twitter, that the incident is "serious and ongoing".

"DP World manages almost 40 percent of the goods flowing in and out of our country," she said.

The disruption has not prevented containers from being taken off vessels but trucks needed to transport them have not been able to drive in or out of the terminals, DP World senior director Blake Tierney said.

Tierney said in a statement the company has made "significant strides" working with cybersecurity experts and is testing key systems "crucial for the resumption of regular freight movement".

The company was seeking to restore normal operations "as quickly and safely as possible", he said, and was investigating "the nature of data access and data theft".

"DP World Australia is working hard to assess whether any personal information has been impacted," Tierney said.

Australian Federal Police have said they are investigating the incident.

National Cyber Security Coordinator Darren Goldie said on X on Saturday the disruption to port operations is "likely to continue for a number of days and will impact the movement of goods into and out" of the country.

"DP World Australia has advised it has restricted access to its Australian port operations while it investigates the incident," he said.

Lucrative target 

After emergency meetings on Saturday, Goldie again convened the National Coordination Mechanism on Sunday with representatives from government, maritime and logistics sectors to manage the government's response.

Australia's National Emergency Management Agency also attended the talks.

Goldie, an air marshal in the Royal Australian Air Force, was appointed the inaugural national coordinator last July in response to several cyber attacks.

Cybersecurity experts have said inadequate safeguards and the stockpiling of sensitive customer information have made Australia a lucrative target for hackers.

Medibank, Australia's largest private health insurer, said in November 2022 that hackers had accessed the data of 9.7 million current and former customers, including medical records related to drug abuse and pregnancy terminations.

Just two months earlier, telecom company Optus fell prey to a data breach of similar scale in which the personal details of up to 9.8 million people were accessed.

Those two incidents were among the largest data breaches in Australian history.

Optus, Australia's second-largest phone provider, apologised to its more than 10 million customers last week over a "technical network outage" that crashed electronic payments, disrupted phone lines used by emergency services and stopped people accessing government services.

The Australian government has launched an investigation into that unexplained glitch, although it has not been described as a cyber attack.

There were 76,000 cybercrimes reported to the Australian Cyber Security Centre last year, although experts warn many more go unreported.