An Asics store manager has apologised and says a full investigation is under way after pornography appeared on large TV screens above its Auckland central shop.

A spokeswoman at Asics head office has also confirmed the company has contacted police and Netsafe over the incident.

The store manager, who gave his name only as John, said the incident happened because of a cybersecurity breach - he was "100 per cent sure" the explicit videos had not been uploaded by one of his staff.

Shoppers on Queen St, including young children, had been shocked to see pornography playing on the large screen outside the sportswear shop on Shortland St which witnesses say ran from 1am to 10am when staff turned up for work.

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"Head office and our IT team have begun a full investigation into what happened and who uploaded the page," John said.

"Screens were immediately turned off to the units immediately when they turned up for work on Sunday. Clearly this is an embarrassing situation, and Asics has apologised through our website and also by email to our customer database."

Tanya Lee, a mother who was on her way to breakfast with her 7-year-old son said the content was "totally inappropriate and offensive".

"I took a second look because I just couldn't believe what I was seeing," she said.

"[It's] not something you want kids exposed to and it's also embarrassing for Auckland as a tourist destination."

Security officer Dwayne Hinango said he witnessed the video playing for almost two hours, but other witnesses say it had been running since 1am.

"Some people were shocked, but others just stopped and watched," Hinango said.

In a media statement, Asics said the Shortland St store "was subject to a cyber security breach".

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"We are currently investigating the situation and working to mitigate it happening again in future," the statement said.

"We sincerely apologise to those who saw the content."