The test, one of the most provocative ever from the reclusive state, appeared to have been of a recently developed intermediate-range Hwasong-12 missile, experts said. It came as U.S. and South Korean forces conduct annual military drills on the peninsula, to which North Korea strenuously objects, as reported by Reuters.
Earlier this month, North Korea threatened to fire four Hwasong-12 missiles into the sea near the U.S. Pacific territory of Guam after U.S. President Donald Trump warned Pyongyang would face "fire and fury" if it threatened the United States.
North Korea has conducted dozens of ballistic missile tests under young leader Kim Jong Un, the most recent on Saturday, but firing projectiles over mainland Japan is rare.
Read alsoNorth Korea fires missile over Japan's territory, reports say"North Korea's reckless action is an unprecedented, serious and a grave threat to our nation," Japanese Prime Minister Shinzo Abe told reporters.
Abe said he spoke to Trump on Tuesday and they agreed to increase pressure on North Korea. Trump also said the United States was "100 percent with Japan," Abe told reporters.
The United Nations Security Council would meet later on Tuesday to discuss the test, diplomats said.
Earlier this month, the 15-member Security Council unanimously imposed new sanctions on North Korea in response to two long-range missile launches in July.