A shell exploded inside a tank during an exercise Tuesday at a Japanese army training area in southern Japan, killing three soldiers and injuring one, officials said.

The deadly blast occurred when the three soldiers — a tank commander, a gunner and a safety officer — were inside a gun turret on a Type 10 main battle tank during a live fire exercise with two other tanks at the Hijudai Training Area in the southern prefecture of Oita.

The fourth occupant of the tank, the driver, survived but was injured, officials said.

Masayoshi Arai, chief of staff of the Japan Ground Self-Defense Force, said the army has suspended live-fire exercises using Type 10 and Type 90 tanks that use the same shells while officials investigate the cause and other details of the accident.

“We will promptly determine the cause so that we can take preventive measures,” Arai said.

Type 10 is Japan's newest tank, which it started deploying in 2011.

It comes as Japan on Tuesday scrapped a ban on lethal weapons exports, a major change in its postwar pacifist policy as the country seeks to build up its arms industry amid worries over Chinese and North Korean aggression.

The approval by Prime Minister Sanae Takaichi's Cabinet of the new guideline clears a final set of hurdles for many arms sales, including of Japanese-developed warships, combat drones and other weapons.

China criticized the change in policy, but it has been largely welcomed by Japanese defense partners like Australia and attracted interest from Southeast Asia and Europe.Opponents say the change violates Japan's pacifist constitution and will increase global tensions and threaten the safety of the Japanese people.

The new policy will "ensure safety for Japan and further contribute to the peace and stability in the region and the international society as the security environment around our country rapidly changes," Chief Cabinet Secretary Minoru Kihara told reporters.

"The government will strategically promote defense equipment transfers to create a security environment that is desirable for Japan and to build up the industrial base that can support fighting resilience."