The launches were North Korea's first known missile testing activities in about a month. Outside experts earlier predicted North Korea would extend its run of missile tests and intensify its warlike rhetoric ahead of the US presidential election in November to boost its leverage in future diplomacy.

Japan's Defence Ministry said North Korea fired three missiles, two together at 7:44 am and the other about 37 minutes later. Japanese Prime Minister Fumio Kishida told a parliamentary session that the North Korean missiles landed in the waters between the Korean Peninsula and Japan, all outside of Japan's exclusive economic zone, and that no damage or injuries have been reported.

Kishida denounced North Korea's repeated ballistic missile tests as acts "that threaten the peace and safety of Japan, the region and the international society". He said Japan strongly protested against North Korea over its testing activities, saying they violated UN Security Council resolutions that ban the North from engaging in any ballistic activities.

South Korea's military said it also detected "several" suspected short-range ballistic launches by North Korea on Monday morning. The Joint Chiefs of Staff called the launches "clear provocation" that threaten peace on the Korean Peninsula. It said South Korea will maintain readiness to repel any provocation by North Korea, based on its solid military alliance with the United States.

According to Japan and South Korean assessments, the North Korean missiles fired from its capital region travelled a distance of 300-350 kilometres (about 185-220 miles) at the maximum speed of 50 kilometres (about 30 miles) per hour.

The US State Department condemned the launches, saying they pose a threat to the North's neighbours and undermine regional security. A State Department statement said the US commitment to the defence of South Korea and Japan remain "ironclad".

The US stations a total of 80,000 troops in South Korea and Japan, the backbone of its military presence in the Asia-Pacific region.

During the South Korea-US military drills that ended on Thursday, North Korean leader Kim Jong Un guided a series of military training exercises involving tanks, artillery guns and paratroopers and called for greater war fighting capabilities. The 11-day South Korean-US drills involved a computer-simulated command post training and 48 kinds of field exercises, twice the number conducted last year.

The North didn't perform any missile tests during its rivals' training, however. Its missile tests are considered much bigger provocations as North Korea has been pushing hard to mount nuclear warheads on its missiles targeting the US mainland and its allies. Many experts say North Korea already has nuclear-armed missiles capable of reaching all of South Korea and Japan, but it has yet to have functioning long-range missiles that can strike the US mainland.

Before Monday's launches, North Korea last carried out missile tests in mid-February by firing cruise missiles into the sea.

Animosities on the Korean Peninsula remain high in the wake of North Korea's barrage of missile tests since 2022. Many of the tests involved nuclear-capable missiles designed to attack South Korea and the mainland US. The US and South Korean forces have responded by expanding their training exercises and trilateral drills involving Japan.

Experts say North Korea likely believes a bigger weapons arsenal would increase its leverage in future diplomacy with the United States. They say North Korea would want to win extensive sanctions relief while maintaining its nuclear weapons.

Worries about North Korean military moves have deepened since Kim vowed in a speech in January to rewrite the constitution to eliminate the country's long-standing goal of seeking peaceful unification of the Korean Peninsula and to cement South Korea as its "invariable principal enemy". He said the new charter must specify North Korea would annex and subjugate the South if another war broke out.

Observers say North Korea may launch limited provocations along its tense border with South Korea. But they say the prospects for a full-scale attack by North Korea are dim as it would know its military is outmatched by the US and South Korean forces.