The Ministry of Foreign Affairs is advising New Zealanders to leave Tokyo and northern Honshu unless their presence there is essential.
It says in the latest update of its travel advisory that people should either go to other parts of Japan, or leave the country.
Previous advice had been to consider leaving the area.
The ministry continues to tell people to stay at least 80km away from the Fukushima nuclear reactors, saying the situation there is unstable and it is not clear what will happen.
It says any New Zealanders who find themselves stranded in Japan should contact the embassy there, and says consular representatives are based at Tokyo's Narita airport for those needing consular assistance.
For people wanting to move south of Tokyo, the ministry says the bullet trains are leaving every 10 minutes, and are able to carry 1,600 people at a time.
Change for replacement passports
Meanwhile, New Zealanders who have lost their passports in tsunami and quake damaged areas of Japan are being forced to pay for emergency replacements.
Fane Walter was forced to flee her home in the coastal town of Tomioka, 5km from the damaged Fukushima nuclear power plants.
She says she left her passport in the rush to evacuate and the New Zealand Embassy in Japan is being very unhelpful.
The Ambassador, Ian Kennedy, says making tsunami and quake victims pay for new passports is tough, but the embassy has done all it can to make the process easier.
He told Morning Report staff have tried to be compassionate and he believes discussions with Ms Walter ended amicably.
A spokesperson says in an emergency, the ministry can issue a travel document based on an arrangement to repay the ministry.
The ministry and the Immigration Service can also work together to issue a passport waiver for a direct flight to New Zealand.
Mr Kennedy says New Zealanders wanting to leave Japan will also have to pay for flights on commercial airlines, although the embassy has a small pool of money available for people who cannot raise the funds.
The Ambassador says the last person his embassy had concerns about in Japan has been located.
NZers still in zone
There are still a few New Zealanders in the 80km zone around the Fukushima nuclear plant although several others have already left the area.
One of those who made the decision to leave is Te Puoho Katene, who has brought his young family back to New Zealand.
He told Morning Report that Japanese reporting of what is happening in Fukushima is quite different to what the rest of the world is hearing.
He says there is a sense in Fukushima that things are under control, although there is an undercurrent of fear.