New Zealand is one of the first countries to respond to a call for help from Japan after a tsunami swept over the north of the country, killing hundreds and wiping out thousands of homes.
Prime Minister John Key announced today six urban search and rescue team members would leave tonight after Japan asked for help, and the balance of the 48 team members would probably leave tomorrow.
It was too early to say how long they would be there but it could be two or three weeks.
He said the early call for help showed the New Zealand team was world class.
"They proved that and when the Japanese team came and worked alongside them in Christchurch they saw first hand just how good our people are and it is a feather in their cap that despite the fact that we are dealing with a massive earthquake in Christchurch, the Japanese have turned to New Zealand and asked us for support.
"We obviously want to give that support to the people of Japan. They have been very kind and generous to us."
He said 240 people had been confirmed dead in Japan and a further 720 were missing following yesterday's magnitude 8.9 quake, which triggered a massive tsunami.
"Those numbers could change dramatically," Mr Key said today.
No New Zealanders had been registered as fatalities or casualties.
"I would hasten to add New Zealanders are notorious for not registering when they go to Japan. At any one time we anticipate there would be 5000-10,000 New Zealanders in Japan.
"We will continue to monitor what is going on but we can't rule out New Zealanders haven't been caught up in this tragedy."
It could take some time before it was known how many New Zealanders were in Japan, Mr Key said.
The Japanese Government request for help recognised New Zealand's expertise in search and rescue, he said.
"We want to offer whatever support we can.
"We are conscious of the fact that we are dealing with our own crisis in Christchurch."
Mr Key said he had been assured by search and rescue authorities that sending a team from New Zealand would not leave New Zealand under resourced in Christchurch and "that we are able to respond if we needed to, to any further aftershocks in Christchurch".
New Zealand sent its heartfelt sympathy to the people of Japan, he said.
Immediately after the magnitude 6.3 quake in Christchurch on February 22, the Japanese Prime Minister Kan Naoto was "very kind and gracious in ringing me ... and obviously we would want to do the same".
Labour leader Phil Goff also expressed sympathies with the people of Japan.
"Our hearts go out to the people of Japan at this time of tragedy, particularly to those living in the north-eastern region of the country which has been so badly damaged by the tsunami.
"It is only fitting that we offer the same helping hand to our Japanese friends as they gave us in the immediate aftermath of the recent devastating quake in Christchurch," he said.
"It is going to take a world-wide effort to help the country recover from this disaster.
"My thoughts are also with those New Zealanders living or travelling in Japan at the moment. I hope they are all safe and well."