TOKYO - Three people were killed and one injured after an ammunition explosion occurred during a training exercise on Tuesday morning at a Japan Ground Self-Defense Force (GSDF) training area in Oita Prefecture, public broadcaster NHK reported.

The explosion took place during training at the GSDF's Hijudai maneuver area in southwestern Japan, where multiple personnel were caught in the blast, the report said, citing sources related to the defense ministry.

The unit conducting the training is believed to have been a tank unit.

The GSDF is investigating the details of the incident, including the condition of those involved and the cause of the explosion.