Lyttelton Port, Christchurch's maritime hub, will suspend operations tonight to secure its IT system over threats from the global WannaCry ransomware cyber attack.

In a statement on its website, the council-owned port said an IT outage will be in place from 11pm Tuesday until 7am on Wednesday to let its IT department install measures "to limit the risk of attack to our IT systems" in response to the ransomware attack.

The outage will give the port's system the required security to respond to the threat.

"Due to this outage, operations will be temporarily suspended during this time.

There will be no R&D (receiving and delivering) throughout this period," the port's website said.

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"The outage will also affect use of the N4 Export Pre-advise system (which is used to help manage containers). There are no shipping services scheduled to be worked during this period."

The WannaCry ransomware attack hit computer systems around the world in what has been reported as the biggest international ransomware campaign to date.

Ransomware blocks a user's access to a computer and demands payment to release the device, according to the government's Computer Emergency Response Team (Cert NZ) website.