North Korea launched several projectiles, including a ballistic missile, into the Yellow Sea on Tuesday, South Korea's military said.
South Korea's Joint Chiefs of Staff said they had detected the launches of "several projectiles", including a short-range ballistic missile, into the Yellow Sea from the North Korean city of Chongju at around 1:00 pm local time.
The Yellow Sea is the body of water separating the Korean peninsula from China.
The missiles flew about 80 kilometres, Seoul's military said, adding that it was analysing their specifications and flight range, and had "strengthened surveillance and vigilance in preparation for possible additional launches."
South Korea, its main security partner the United States, and Japan were "maintaining a state of full readiness" and closely sharing intelligence, Seoul's military said.
The launch was North Korea's first for 37 days and its eighth this year.
Pyongyang has conducted a flurry of missile tests in recent weeks and analysts have said the diplomatically isolated state may be trying to take advantage of eroding international norms to cement its nuclear status.
The North has also repeatedly shunned efforts by the South Korean government to improve relations, repeatedly calling Seoul its most "hostile" adversary.
Earlier this month, the North removed all references to reunification with the South from its constitution, underscoring Pyongyang's push for a more hostile policy towards Seoul.
In April, Pyongyang conducted another such test to "verify the characteristics and power of a cluster bomb warhead," its state media said at the time.
South Korea's Yonhap news agency reported last week, citing unnamed government sources, that Chinese President Xi Jinping would likely visit North Korea sometime this week.
China is North Korea's main economic and political backer, though Pyongyang has drawn closer to Russia in recent years, sending thousands of troops to help Russia push back a surprise Ukrainian incursion into the Kursk region.
Analysts say the North has received economic and military technology assistance from Russia in return for sending troops and ammunition to help its war effort.
