Covid Response Minister Chris Hipkins has confirmed that flights from New South Wales to New Zealand will be paused from midnight tonight for 48 hours.

Speaking to media this evening, Hipkins said it had been a "finely-balanced decision" and he was aware it could disrupt people's plans for travel to or from NSW. He also warned the cessation of flights could go on longer.

"If further information comes to light that means we need to extend that, we have the ability to do that."

He said about 6000 people who have travelled from NSW in the past six days will be contacted and contact traced.

New Zealand health officials had been in talks with Australian authorities this afternoon about the community cases of Covid-19 in Sydney.

A man from Sydney's eastern suburbs with no known link to the border tested positive for the virus yesterday, while his wife tested positive today.

Hipkins said this evening that the Sydney case was likely to have come from managed isolation but that there was no obvious link as to how it got into the community.

"Sometimes it takes a wee while to identify a train of transmission.

"They will be working as hard as they can to try and identify that."

He said it was likely to have been seven or eight days since the source of infection arrived in Australia.

The NSW government announced it would to re-introduce a raft of restrictions for Greater Sydney following the cases.

Restrictions will apply until at least Monday and limit household guests to 20, make masks compulsory in indoor public venues and on public transport, and restrict aged care visitation to two people.

RNZ.