The likely cause of the crash was a collision between two SH-60K helicopters, each carrying four crew members, during nighttime anti-submarine exercises in an area east of Tori-shima Island in the Pacific, Kihara told reporters.
The military has already found what is believed to be helicopter debris during a post-accident search, he said, adding that the cause of the accident was still unknown.
Earlier, the Japanese Defense Ministry said that that the SH-60K helicopter stopped communicating in the area of Tori-shima Island near the Izu Island chain, a minute later the helicopter sent a distress signal.
About half an hour later, another similar helicopter stopped communicating from the same area, the ministry said.