North Korea fired a ballistic missile toward the sea on Wednesday, the South Korean military said, according to the Yonhap news agency.
South Korea's Joint Chiefs of Staff said it detected the launch but gave no details, saying an analysis is under way.
The office of Japanese Prime Minister Fumio Kishida confirmed on social media platform X that North Korea launched a suspected ballistic missile.
"The suspected ballistic missile from North Korea is not expected to reach Japan," it said of the projectile filed toward the East Sea, also known as the Sea of Japan.
This launch comes amid increased cross-border tension as the reclusive communist state has been sending balloons carrying garbage into South Korea.
North Korea's last missile launch prior to this one came on May 30, when Seoul accused Pyongyang of firing a volley of around 10 short-range ballistic missiles.
One day later, North Korean state media released images of leader Kim Jong Un supervising tests of a multiple rocket launcher system.
Analysts have suggested the nuclear-armed North could be testing and ramping up production of artillery and cruise missiles before sending them to Russia for use in Ukraine.
In a report last month, the Pentagon said it had confirmed this behaviour.
North Korea has sent more trash-filled balloons southward this week, Seoul's military said Tuesday, the latest in a series of border barrages that have sparked a tit-for-tat propaganda campaign.
Pyongyang has already sent more than a thousand balloons carrying trash in what it says is retaliation for balloons carrying propaganda criticising Kim's rule floated north by activists.
In response, Seoul has fully suspended a tension-reducing military deal and restarted some propaganda broadcasts from loudspeakers along the border.
Kim Jong Un's sister and key government spokeswoman Kim Yo Jong warned this month that Seoul would "undoubtedly witness the new counteraction of the DPRK" if the leaflet drops and loudspeaker broadcasts continued.