North Korea on Wednesday fired three short range ballistic missiles, Seoul said, prompting a rare air raid warning for a South Korean island.
"North Korea fired three short-range ballistic missiles toward the East Sea," the Joint Chiefs of Staff said in a statement, referring to the body of water also known as the Sea of Japan.
An air raid warning was issued for the island of Ulleungdo, JCS said, which was flashed on national television and told residents to "evacuate to the nearest underground shelter".
The military said one of Pyongyang's missiles had landed in international waters south of the Northern Limit Line, the disputed maritime border between the two countries.
South Korean President Yoon Suk-yeol called a meeting of the National Security Council over the launch, which analysts said was one of the most "aggressive and threatening" in many years.
Japan also confirmed the launch of suspected North Korean ballistic missiles, with the coastguard warning vessels to take care.
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Japanese Prime Minister Fumio Kishida told reporters: "As we see tensions rising in the Korean Peninsula, I would like to hold a national security meeting as soon as possible."
Pyongyang's latest launch comes as Seoul and Washington stage their largest-ever joint air drills, dubbed "Vigilant Storm", which involve hundreds of warplanes from both sides.
Pak Jong Chon, a high-ranking official in North Korea, said the drills were aggressive and provocative, according to a report in state media Wednesday.
Pak said the name of the exercises harks back to Operation Desert Storm, the US-led military assault on Iraq in 1990-1991 after it invaded Kuwait.
"If the US and South Korea attempt to use armed forces against the (Democratic People's Republic of Korea) without any fear, the special means of the DPRK's armed forces will carry out their strategic mission without delay," he said.
"The US and South Korea will have to face a terrible case and pay the most horrible price in history."