Debris believed to be aircraft parts was spotted in the area, about 1,800 kilometers (1,120 miles) southwest of Tokyo, he said.
The government is aggressively building up its defense capability in southwestern Japan in response to China’s increasingly assertive military activity in the region, including Taiwan.
Kyodo News said Japanese coast guard ships also found traces of oil that may be related to the missing helicopter, but officials declined to confirm the report.
Morishita said the helicopter was stationed at a key regional army base in Kumamoto prefecture on the southern main island of Kyushu, and one of its 10 crew members is the division commander, Yuichi Sakamoto.
Morishita said the helicopter disappeared from radar earlier than previously thought.
NHK public television earlier said the helicopter disappeared from radar about an hour after it departed from Miyako island and about half an hour before its scheduled return.
Prime Minister Fumio Kishida said the Defense Ministry is investigating.
