North Korea has fired a rocket towards the South, which crossed the 2 countries' maritime borderline for the archetypal clip since the peninsula's split.
The short-range ballistic rocket landed immoderate 60km (37 miles) from the South's metropolis of Sokcho and triggered air-raid alarms connected Ulleungdo island.
South Korea aboriginal fired 3 missiles successful effect to the North.
Seoul's President Yoon Suk-yeol had called Pyongyang's motorboat an "effective territorial invasion".
Pyongyang fired astatine slightest 10 missiles "east and west" connected Wednesday morning, the South Korean subject said.
Later connected Wednesday, South Korea's subject said it had fired 3 air-to-ground missiles towards northbound of its maritime border, successful effect to the North's launch.
It had earlier declared that subject could not "tolerate this benignant of North Korea's provocative act, and volition strictly and firmly respond nether adjacent South Korea-U.S. cooperation," said the Joint Chiefs of Staff successful a statement.
They added South Korean President Yoon Suk-yeol had ordered a "swift response" to the latest aggression.
Both South Korea and Japan's leaders person called nationalist information meetings successful effect to North Korea's latest firings.
Both countries had recorded the missiles conscionable earlier 09:00 (00:00 GMT) connected Wednesday, including the 1 which breached the Northern Limit Line - the defacto maritime border.
That rocket had landed successful waters 26km (16 miles) southbound of the demarcation line, 57km eastbound of the South Korean metropolis of Sokcho and 167km north-west of Ulleungdo island.
This was "very antithetic and unacceptable" arsenic it had fallen adjacent to "territorial waters southbound of the Northern Limit Line for the archetypal time" since the peninsula was divided, said Kang Shin-chul, manager of operations for the Joint Chiefs of Staff.
The missiles travel a time aft Pyongyang warned the US and South Korea to halt its associated subject drills this week astir the peninsula.
On Tuesday, North Korea had threatened that if the allies didn't halt their drills, it would instrumentality "powerful" measures.
North Korea's launches connected Wednesday follows a blitz of missiles it fired past period which it said were besides successful effect to US, South Korea and Japan associated drills. It had described its effect arsenic a "simulation" for a atomic onslaught connected the South.