Japan's military is searching for a naval training helicopter that went missing with three people on board Thursday, a spokesman said.

Ground commanders lost contact with the chopper at about 11:00 am (0200 GMT), when it was in the air above Kagoshima prefecture in southwestern Japan, a spokesman for the Maritime Self-Defense Force, Japan's navy, told Agence France Presse.

"We are searching for an aircraft with three crew members including a trainee on board, and are investigating the cause of the incident," he said.

The crew is part of a unit that trains pilots, he said.