Seoul, South Korea - South Korean fighter jets fired three air-to-surface missiles on Wednesday in response to a renewed bout of missile launches by North Korea.

Pyongyang fired more than a dozen missiles from its eastern and western coast, including one that crossed the maritime border with South Korea in the morning and landed in the sea just less than 40 miles from the coast, the South Korean military said on Wednesday.

Seoul responded by firing three air-to-surface missiles from fighter jets into the open sea north of the de facto maritime border, the military said.

South Korean news agency Yonhap cited the Joint Chiefs of Staff (JCS) as saying that one North Korean missile flew toward the eastern South Korean island of Ulleungdo before crashing into international waters in the Sea of Japan.

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An alert was sounded on the island and residents were told to seek out air raid shelters.

Another missile dropped into waters east of the city of Sokcho, Yonhap reported.

This was the first time since the end of the Korean War in 1953 that a North Korean missile had landed near South Korean territorial waters, a Defense Ministry spokesman said in Seoul.

President Yoon Suk Yeol accused Pyongyang of provocation, stating that it was "practically a violation of our territory by a rocket that crossed the Northern Limit Line (NLL) for the first time since the division" of the country.

North Korea would pay a high price, he added.

The NLL was drawn unilaterally by the US-led UN Command after the 1950-53 Korean War. It is not recognized by North Korea.

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Also on Wednesday, North Korea fired about 100 artillery shells along the maritime border line in the east, according to South Korean sources. They fell in a buffer zone.

The new North Korean missile tests and artillery shots were seen in South Korea as a reaction to the largest air exercise to be conducted by South Korean and US forces in several years.

The joint air exercise, involving some 140 aircraft from South Korea and 100 aircraft from the US Air Force, kicked off on Monday.

North Korea has accused both countries of "reckless" military provocation and threatened countermeasures.

The situation on the Korean peninsula is currently very tense. Nuclear-armed North Korea has conducted a string of missile tests in the past few weeks.

The government in Pyongyang has said in its own statements that the tests were intended to simulate the firing of tactical nuclear weapons at South Korean airfields.

South Korea said their analyses confirmed that seven of the North Korean missiles fired on Wednesday were short-range ballistic missiles (SRBM). The remainder could have been SRBMs or surface-to-air missiles.

North Korea regularly accuses the United States of preparing an attack through its maneuvers with South Korea, which both countries deny. The US has 28,500 soldiers stationed in South Korea.