Flow-on effects from a cyber attack are affecting Australia's second-largest port operator.

DP World Australia, which is responsible for 40 percent of maritime freight, stopped internet access to all its ports on Friday, halting goods movement in and out of the country.

Australian correspondent Oliver Peterson says the ports in Perth and Brisbane have just restarted operations.

But he says Sydney can't accept export cargo for another two weeks.

"So you can imagine the massive delays this is going to create for businesses well into the lead-up to Christmas, they believe they'll be running out of stock in the next few weeks."

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