The first missile fired by North Korea since the peninsula’s division to cross the two nations’ maritime boundary was fired toward the South.
The short-range ballistic missile caused air-raid alerts on Ulleungdo island and landed around 60 kilometers (37 miles) from the South Korean city of Sokcho.
The launch by Pyongyang was referred regarded as an “effective territorial invasion” by President Yoon Suk-yeol of Seoul.
The South Korean military reported that Pyongyang launched at least 10 missiles “east and west” on Wednesday morning.
The Joint Chiefs of Staff had previously stated that the military could not “tolerate this kind of North Korea’s provocative act, and will sternly and decisively respond under close South Korea-U.S. cooperation.”
They also said that Yoon Suk-year, the president of South Korea, has directed a “rapid response” to the most recent incident.
In response to North Korea’s most recent firings, the leaders of South Korea and Japan have scheduled national security meetings.
Both nations had missiles reported just before 9:00 (00:00 GMT) on Wednesday, including the one that crossed the de facto maritime border known as the Northern Limit Line.
The missile had landed in waters 26 kilometers (16 miles) south of the line of demarcation, 57 kilometers (km) east of the city of Sokcho in South Korea, and 167 kilometers (km) northwest of Ulleungdo island.
Since the peninsula was divided, this has “fallen very unusually and unacceptably close to territorial seas south of the Northern Limit Line for the first time,” according to Kang Shin-Chul, head of operations for the Joint Chiefs of Staff.
The launch of the missiles follows Pyongyang’s warning to the US and South Korea to halt their joint military exercises this week near the peninsula.
If the allies don’t stop their drills, North Korea has warned to take “powerful” action on Tuesday.
The launches by North Korea on Wednesday come after a barrage of missiles it fired last month, which it claimed was also in reaction to joint drills by the US, South Korea, and Japan. It described its response as a “simulation” of a nuclear assault on the South.