UPDATE 7.50AM: The Prime Minister says genome sequencing hasn't linked the latest Covid-19 community cases to anyone in managed isolation.

The three new community cases of COVID-19 announced yesterday are the UK strain of the virus, Jacinda Ardern told Morning Report.

Sewage tests will be undertaken in Auckland and Taranaki today to see if it can detect any traces of COVID-19, says Ardern.

A Ministry of Health spokesperson says the results of genomic sequencing for the first two Auckland February cases is now available.

"The results, which came through from ESR overnight, show the COVID-19 variant B1.1.7 first detected in the UK.

"The results from these cases do not link directly to any other positive cases detected in New Zealand to date.

"ESR is now conducting a scan of the international genome database to see if there is a match."

Lockdown restrictions in Auckland started at midnight and will last three days, although the government will revise the status daily. The rest of the country is under alert level 2.

Police say Auckland boundaries will be set mostly in the same locations as the last time the city was in alert level 3 in August, to ensure there is no non-essential movement through the region.

Auckland mayor Phil Goff says travel exemptions will be made for those needing to get home.

Under the restrictions, Aucklanders need to stay home, and should also work from home if possible.

Non-essential shops will close, and schools and early childhood centres will only be open to children whose parents cannot work from home.

Australia has suspended its quarantine-free travel corridor. People flying from New Zealand from Monday to Wednesday will be required to quarantine for 14 days.

A police checkpoint at Mercer, Auckland. Photo: RNZ.

Checkpoints in and out of Auckland are in place after the city went into level three lockdown at midnight.

The boundaries will be set mostly in the same locations as the last time Auckland was in Alert Level 3 in August.

Eight checkpoints on the outskirts of Auckland will be stopping vehicles and questioning drivers, ensuring there is no non-essential movement through the region, says a police spokesperson.

"From midnight, anyone attempting to travel across the regional boundaries should expect to be stopped and asked for proof of essential travel.

"The exemption process will run the same way as it has previously."

More information is available on the COVID-19 website.

For the latest information, follow the live blog below.

Police will also be highly visible across the region to provide reassurance and to educate people and ensure they are aware of the restrictions in place.

Police Commissioner Andrew Coster says this is not new territory for police or the public, and learnings from last time have allowed staff to mobilise quickly to respond to the change in alert levels.

'We will continue work with a graduated response, starting with education.

We are once again asking the public be safe and abide by the alert level restrictions for their region.

'In Auckland, we will continue be visible and provide assurance to the community, and to checkpoints around the region's Super City boundaries.”

Police staff have been reminded about exercising good hygiene and social distancing practises, and we have issued a directive to our Auckland staff that they must wear masks when dealing with the public, and other PPE gear as necessary.

All front counters in Tamaki Makaurau are closed to the public with the exception of Henderson (Waitemata), College Hill (Auckland City) and the Counties Manukau Hub, which are all open 24/7 but with restricted access.

North Shore Policing Centre will also be open 7am to 10pm, seven days a week, with restricted access.

Throughout the rest of the country most front counters are open, but with restrictions to protect our staff and those coming into the building.

Our Alert Level 2 safety measures focus on physical distancing, hygiene standards, and contact registers.

The 105 Police non-emergency line has been experiencing high demand.

People are being encouraged to visit the police website where possible.

You can report non-emergency situations online at www.police.govt.nz/105support or call 111 if it's an emergency.

For the latest information and updates on the Alert Level restrictions visit covid19.govt.nz.

Australia has suspended its quarantine-free travel corridor. People flying from New Zealand from Monday to Wednesday will be required to quarantine for 14 days.

Prime Minister Jacinda Ardern say the new community cases are not linked to an MIQ case and are a UK varient of the virus.