At 11.59pm on Wednesday, the country will go into full lockdown as New Zealand moves to Covid-19 alert level 4.

Prime Minister Jacinda Ardern yesterday said the lockdown would be for four weeks and after that time could be extended, if needed.

This morning, Ardern told Morning Report that she will look at tightening up restrictions for returning travellers in the next 24 hours.

"We are looking at alternative ways to add that extra layer of guarantee," she said.

She said the majority of New Zealand's cases have been New Zealanders who have had overseas travel.

"You identify issues at the border."

The full lockdown comes as more Covid-19 cases were announced yesterday. There are now 102 confirmed cases in New Zealand.

As NZ prepares for the lockdown, supermarkets have been urging people to calm down and stop panic buying.

A spokesperson for Countdown supermarkets, Kiri Hannifin, said the supermarket chain was selling three times as much toilet paper in a day than it would in a week - and restocking it was a waste of space in trucks which could be carrying food.

Meanwhile, tourists still in New Zealand are being urged to get home as popular transit airports start to close their doors.

If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs)