Japan's military said the missile landed in waters outside its exclusive economic zone, while South Korea's military, which often accuses the North of exaggerating its capabilities, said it travelled more than 700 kilometres.
Authorities announced a revised, higher death toll on Tuesday after search and rescue crews located the bodies of two more people. Six others are still reported missing.
Japan is sharing decades of disaster management expertise with Vietnam through infrastructure, education and early warning projects backed by The Japan International Cooperation Agency (JICA) and UNESCO.