North Korea has fired a short-range ballistic missile, its third missile test in as many weeks.
The Scud flew about 450km (280 miles) before landing in Japanese waters, prompting Japan to lodge a protest.
Pyongyang has repeatedly defied a UN resolution banning all nuclear and missile activity, and has ramped up the pace of its tests in recent months.
Seoul and Tokyo both condemned the launch. Japan’s leader said Pyongyang’s provocations would not be tolerated.
“As we agreed at the recent G7, the issue of North Korea is a top priority for the international community,” Prime Minister Shinzo Abe said. “Working with the United States, we will take specific action to deter North Korea.”
In South Korea, President Moon Jae-in, who took office earlier this month, summoned the national security council to discuss the launch.
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The US Pacific Command said the missile was launched from Wonsan in North Korea and flew for about six minutes before landing.
Japan’s top government spokesman Yoshihide Suga told reporters that the missile landed in an area between Japan’s Sado and Oki islands, in the country’s exclusive economic zone.
A spokesman for South Korea’s military said the missile reached an altitude of 120km. “An analysis is under way on the specific number” of missiles fired, the spokesman said, indicating that more than one could have been launched.
North Korea has a large stockpile of short-range Scud missiles developed by the Soviet Union. Modified versions of the Scud missiles can have a range of 1,000km.
The other two recent launches were of medium to long-range missiles, both of which the North claimed as “successful” tests.
The first of those launches was hailed by Pyongyang as a new type of rocket capable of carrying a nuclear warhead. It said it was a demonstration of the North’s longest-range nuclear-capable weapon yet.
Pyongyang has been testing its missiles at an unprecedented pace. Experts fear the tests indicate progress towards Pyongyang’s ultimate goal of putting a nuclear warhead on a missile that could strike the continental US.
The latest launch came a day after North Korea’s state media reported the test of a new anti-aircraft weapon system, and released pictures of leader Kim Jong-un watching the test.
North Korea says its weapons programme is necessary to counter US aggression.
Last month Vice-Foreign Minister Han Song-ryol told the BBC it would be “conducting more missile tests on a weekly, monthly and yearly basis”.