NORTH Korea has fired three missiles, including one long-range ICBM, in the latest provocation by Kim Jong-un's generals.
The long-range missile was sent in the direction of Japan, triggering air raid sirens in the country.
Military chiefs in Seoul said Pyongyang had fired an "unspecified ballistic missile," believed to be a Hwasong-17.
North Korea reportedly fired two short-range ballistic missiles from Goksan in North Hwanghae province.
The third missile flew to an altitude of 150km, covering a range of 500km, according to Japan's Defence Minister Yasukazu Hamada.
All three fell in the Sea of Japan outside Japan's exclusive economic zone, Hamada said.
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It comes hours after an earlier North Korean missile launch sparked terror in Japan, sending people scrambling for bomb shelters.
South Korea responded to the provocation by Kim Jong-un by announcing the extension of air drills with the United States.
Pyongyang branded the move by the South "an irrevocable and awful mistake".
It marks the seventh firing of an ICBM by the North this year, the first since late May.
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Thursday's long-range missile ultimately failed and broke apart over the Sea of Japan before falling short in the ocean.
But had it failed over Japanese territory, it could well have struck an inhabited area, sparking a major international crisis.
Footage from Joetsu City in Japan's Niigata Prefecture filmed on Thursday shows sirens blaring with residents being warned to stay inside.
Residents in the northern Japanese prefectures of Miyagi, Niigata, and Yamagata were ordered to go inside firm buildings or underground.
Japanese prime minister Fumio Kishida denounced the missile launches from North Korea in a fiery response.
"The continued firing of these weapons, day after day, is an outrage and cannot be tolerated," he said.
Washington also condemned the intercontinental ballistic missile launches.
A US State Department spokesman Ned Price said: "This action underscores the need for all countries to fully implement [North Korea]-related UN Security Council resolutions."
There have been no reports of damage or injuries from the areas where the alerts were issued.
Vessels have been urged not to approach the scene of any falling objects in the water, and report any relevant information to the Japanese Coast Guard.
Bullet train services were briefly suspended in the affected regions, but resumed shortly afterwards.
It is the latest provocation from North Korea to its neighbour, after Pyongyang test-fired 25 missiles on Wednesday, including one which crossed the ocean border and entered South Korean territory.
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The launches, involing a mix of short-range missiles - were the most carried out by the communist dictatorship ever in a single day.
Seoul responded by firing three air-to-surface missiles back across its maritime border with the North.