An urgent Cabinet committee meeting is taking place at 4pm where deputy Prime Minister Winston Peters says a full lockdown of the country and the closure of its borders will be discussed.

"We've got to look at all the possibilities,'' he said.

"The consideration of all these issues is imminent.''

"Every day we consider the latest details and facts and today we have eight more cases all to do with travel, so this afternoon full consideration with new information will take place,'' he said.

Earlier today the government raised its travel advice to the highest level, telling New Zealanders not to travel overseas due to Covid-19.

It's the first time the government has advised New Zealanders against travelling anywhere overseas.

Foreign Affairs Minister Winston Peters said this reflected the seriousness of the situation.

"New Zealanders who travel overseas risk contracting Covid-19. At the same time, health care systems in many countries are under strain and do not have the capacity to support foreigners," he said.

Peters also urged all New Zealanders currently travelling overseas to consider returning home immediately.

"Borders are closing. You may not be able to return to New Zealand when you had planned to. You should therefore organise to come home now.

"If you choose to remain overseas despite our advice, the ability of the New Zealand government to provide consular assistance may be limited due to internal travel restrictions and the suspension of services", he said.

Peters said New Zealanders who are long-term residents overseas need to decide what is best for their personal circumstances.

He said those to decide to remain overseas need to ensure they are well prepared and follow advice from the World Health Organisation and local health authorities.

Rescue flight a possibility

RNZ political reporter Jo Moir reports that New Zealanders stuck overseas may be rescued by the government if it comes to that.

Peters said anyone who chooses to travel now is "selfish" given the government has taken the unprecedented step of telling New Zealanders not to travel overseas.

And he said all options are being considered to get people home, including mercy flights.

"Well, we've got to anticipate that if we've got a whole lot of people offshore who can't get home, they may be able to assemble in one place where we can get a plane to them.

"And bring them home and go through all the security measures at the same time,'' he said.

Peters said it was unprecedented to tell New Zealanders not to travel overseas, but it was necessary.

New Zealanders overseas are also encouraged to register on SafeTravel so they can receive updates.

There are 80,000 New Zealanders travelling overseas currently and 20,000 of them are registered with SafeTravel.

He said it's likely the number registering with SafeTravel will continue to increase.

"These are very serious times and we've got to do the best we can to ensure we don't exacebate the problem we've got by adding potential difficulties to it.

"It's a very tough message, it's unprecedented, but we've got to do it,'' he said.

The number of people registered with Safe Travel went from 17,000 to 20,000 overnight.

Peters said he can't forecast when a mercy flight might be needed but a number of organisations are working on it.

He also hasn't ruled out international travel for him and Trade Minister David Parker.

"There are emergency situations where we might have to, in the interests of our long-term trade and keeping connections open, get on a plane and actually secure that,'' he said.

If necessary Peters and Parker will travel and quarantine on their return home.

An urgent Cabinet committee is taking place at 4pm where deputy Prime Minister Winston Peters says a full lock-down of the country and the closure of New Zealand's borders will both be discussed.

"We've got to look at all the possibilities,'' he said.

"The consideration of all these issues is imminent.''

"Every day we consider the latest details and facts and today we have eight more cases all to do with travel, so this afternoon full consideration with new information will take place,'' he said.