A 70-strong rescue team was due to leave Japan on Wednesday for New Zealand's quake-hit city of Christchurch, where at least 23 of its citizens were missing, many feared trapped under rubble.
Japan is one of the world's most earthquake-prone countries and the team includes specialist rescue workers from the coastguard,
police and fire fighting service, doctors and nurses as well as sniffer dogs.
The missing Japanese are English-language students from several schools who were in the city when it was hit by the shallow 6.3 magnitude quake Tuesday that killed at least 75 people and left about 300 missing.
Among the Japanese missing were 10 students from Toyama College of Foreign Languages in the central prefecture of the same name, who were feared trapped under the rubble of the collapsed CTB building housing the King's Education College.
Several other Japanese students and their female teacher were rescued, including one whose crushed leg was amputated, media reports said.
Three Japanese who studied at the same language school were also missing, Kyodo News and other media said. One of them was from the city of Kobe, which suffered a devastating quake in 1995 that killed more than 6,000 people.
Two South Korean students - a brother and a sister in their early 20s - were also missing feared trapped in the same Christchurch language school, South Korea's foreign ministry said in a statement.
South Korean President Lee Myung-Bak on Tuesday sent a message of condolence to New Zealand and pledged to dispatch emergency rescue workers.
Additionally, a Tokyo company that organises studies abroad said it had been unable to contact 10 students who visited New Zealand on one of its tours, according to reports.
The Japanese rescue team was due to leave from Tokyo's Narita international airport on a special Air Self-Defence Force flight in the afternoon, around 0500 GMT (1800NZT), and arrive in New Zealand in the early hours of Thursday.
Japan's Prime Minister Naoto Kan said at an emergency meeting of his cabinet ministers, the second since the quake hit, that he expected the team ``to rescue as many people as possible''.
Like New Zealand, Japan sits on the ``Pacific Ring of Fire'' zone of high seismic activity and is often hit by powerful earthquakes.
New Zealand's ambassador in Tokyo had requested Japan's emergency assistance on Tuesday.
