An 18-year-old trainee shot three fellow soldiers at a firing range on a Japanese army base on Wednesday, killing two of them, officials said.
The suspect was arrested on suspicion of attempted murder at the scene in Gifu prefecture in central Japan.
The teenager allegedly fired a rifle at the soldiers during a shooting exercise at the Hino Kihon firing range, police said.
The Ground Self Defence Force, Japan’s army, confirmed that two of those wounded were later pronounced dead at a hospital.
Army Chief of Staff General Yasunori Morishita said the suspect joined the military in April and the three soldiers were assisting his shooting exercise as instructors.
“An organisation that handles weapons should never allow an incident like this to happen,” Gen Morishita said at a news conference. “As head of the army, I take this very seriously.”
He said he has ordered a temporary suspension of exercises involving shooting and explosives across the country while the army investigates and prepares safety measures to prevent a recurrence.
A number of other people were believed to be participating in the training when the shooting occurred, but details are still under investigation, an army official said.
Japan has been known for its safety, with strict gun control laws, but high-profile violence has occurred in recent years, including shootings and random stabbings on subways and arson attacks, and there is growing concern about homemade guns and explosives.
Prime Minister Fumio Kishida was almost hit by a pipe bomb thrown at an election campaign venue in April.
Former prime minister Shinzo Abe was assassinated in July 2022 by an attacker using a handmade gun.
Last month, a man was arrested after he allegedly shot two police officers dead after killing two women with a knife in Nagano prefecture.
