North Korea fired a missile that flew over Japan and landed in waters off the northern region of Hokkaido early on Tuesday, South Korean and Japanese officials said, marking a sharp escalation of tensions on the Korean peninsula.
The test, which experts said appeared to have been a recently developed intermediate-range Hwasong-12 missile, came as U.S. and South Korean forces conduct annual military drills on the peninsula, against which North Korea strenuously objects.
Earlier this month, North Korea threatened to fire 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.
"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 Japan was seeking an urgent meeting at the United Nations to strengthen measures against Pyongyang. The test was a clear violation of UN resolutions and the government had protested against the move in the strongest terms, he said.
South Korea also condemned the launch. "We will respond strongly based on our steadfast alliance with the United States if North Korea continues nuclear and missile provocations," the South's foreign ministry said in a statement.
North Korea fired what it said was a rocket carrying a communications satellite into orbit over Japan in 2009. The United States, Japan and South Korea considered that launch to have been a ballistic missile test.
"It's pretty unusual," said Jeffrey Lewis, head of the East Asia Nonproliferation Program at the Middlebury Institute of Strategic Studies in Monterey, California. "North Korea's early space launches in 1998 and 2009 went over Japan, but that's not the same thing as firing a missile."
Japan's Chief Cabinet Secretary Yoshihide Suga said the latest North Korean missile fell into the sea 1,180 km (735 miles) east of the Cape of Erimo on Hokkaido.