North Korea fired at least one ballistic missile over the Sea of Japan on Thursday, Seoul's military said, after Pyongyang lambasted Tokyo for beefing up its military stance in the Pacific.
North Korea has repeatedly declared itself an "irreversible" nuclear state since leader Kim Jong Un's 2019 summit with US President Donald Trump collapsed over the scope of denuclearization and sanctions relief.
Tokyo's Defense Minister Shinjiro Koizumi said earlier this week that Japan's military needs to be boosted with a "sense of urgency and crisis", as a new government assessment warned of growing threats from China, Russia and North Korea.
In a statement carried by North Korean state media on Wednesday, Kim Yo Jong -- the powerful sister of leader Kim Jong Un -- said Pyongyang's "leadership will set up additional military options which are obviously due to Japan's transformation".
"Our military detected a short-range ballistic missile launched from the Wonsan area of North Korea at around 5:00 pm (0800 GMT)," South Korea's Joint Chiefs of Staff (JCS) said in a message to news organizations.
The JCS said earlier the missile was launched towards the East Sea, referring to the body of water also known as the Sea of Japan.
Japan's defense ministry also posted on X that "something that may be a ballistic missile has been launched from North Korea."
A separate post shortly afterwards said "there is no longer any impact on the areas around Japan".
Seoul has strengthened surveillance and maintained readiness for possible additional launches while sharing information with its security allies -- the United States and Japan, the JCS said.
North Korea has recently deepened economic and military ties with Russia, supplying troops and munitions for Moscow's war in Ukraine in exchange for financial support, food, energy and military technology, analysts say.
It has also repeatedly branded Seoul -- a security ally of Washington -- its "most hostile" enemy.
According to AFP, Japan's defense ministry declined to comment directly on Kim Yo Jong's Wednesday diatribe but said the country's defense capabilities "remain bare minimum" and "are not meant to threaten other countries".
"Ours isn't the defense meant to wage wars, but to prevent new wars, strictly kept to self-defense and within the scope of our (pacifist) Constitution and international laws," it said in a statement.
Tokyo raised its military expenditure by 9.7 percent to $62.2 billion in 2025 -- equivalent to 1.4 percent of GDP, its highest share since 1958.
China, a key ally of North Korea, has also recently expressed alarm at what it sees as "new militarism" by Japan.
South Korea's dovish President Lee Jae Myung has reversed the stance of his hawkish predecessor since taking power in Seoul in June 2025, offering nuclear-armed Pyongyang talks without preconditions.
The hermetic leadership of North Korea has yet to respond to his repeated offers.
The two Koreas remain technically at war because their 1950-53 conflict ended with an armistice rather than a peace treaty.
