North Korea launched two ballistic missiles eastward early on Wednesday, and both of them appeared to have fallen outside Japan's exclusive economic zone, Japanese Defence Minister Yasukazu Hamada said.
The first missile reached an altitude of 50 km (31 miles) and covered a range of 550 km, while the second one rose as high as 50 km and flew 600 km, Hamada told reporters.
Japan lodged a protest against the missile launches through diplomatic channels, he said.
The firing comes nearly a week after North Korea tested its latest Hwasong-18 intercontinental ballistic missile, a launch Pyongyang said was a warning to the United States and other adversaries.
Wednesday's launch came a day after a U.S. nuclear-armed ballistic missile submarine visited South Korea for the first time since the 1980s.
Also on Tuesday, a U.S. soldier facing disciplinary action fled across the inter-Korean border into North Korea. The soldier is believed to be in North Korean custody, Washington said, creating a fresh crisis between the two foes.