Two Japanese soldiers killed and another injured after a new recruit opened fire at a military training range in central Japan, officials say.
An 18-year-old trainee detained on the spot and arrested on suspicion of attempted murder, police said.
They allege the male shooter fired eight times at instructors during a shooting drill in Gifu on Wednesday.
A 25-year-old man was among those killed, authorities said.
Details about the other victims, in their 20s and 50s, not yet known. But they were all instructors at the facility.
No civilians involved, Japan’s Ground Self-Defence Force said.
They said the shooting had occurred during a live-fire training for new members and potential candidates. The suspect had joined the force in April.
Following the attack on Wednesday, live-fire and explosive training drills suspended across the country, said the chief of Japan’s Self-Defence Forces.
Gun violence remains extremely rare in Japan, but there have been some notable incidents in the past year.
Former Prime Minister Shinzo Abe gunned down at a political rally by a protester last July.
Abe was Japan’s longest-serving prime minister and his death profoundly shocked the country.
Japan again rattled in April when Prime Minister Fumio Kishida escaped unharmed after having a smoke bomb thrown at his campaign event.
On Wednesday, pictures on Japanese media showed police and emergency vehicles blocking off roads around the training facility in Gifu city.
Japan’s Chief Cabinet Secretary Matsuno Hirokazu said he was aware of the shooting, and said the incident was still under investigation.
Japan has strict gun ownership rules, and only allows civilians to own hunting rifles and airguns. People have to undergo a strict exam and mental health tests in order to buy a gun in Japan.