South Korea's military fired a missile barrage into the Sea of Japan in response to the ICBM launch, the first full-range test of Kim Jong Un's most powerful missiles since 2017.

Pyongyang has conducted an unprecedented blitz of nearly a dozen sanctions-busting tests this year. But long-range and nuclear tests have been paused since Kim met then US president Donald Trump for a bout of diplomacy, which collapsed in 2019.

Thursday's launch was a "breach of the suspension of intercontinental ballistic missile launches promised by" Kim, South Korea's President Moon Jae-in said.

"It poses a serious threat to the Korean peninsula, the region and the international community," he said, adding that it was a "clear violation" of UN Security Council resolutions, a charge repeated by UN Secretary-General Antonio Guterres.

The United States also strongly condemned the launch as a Security Council violation that "needlessly raises tensions and risks destabilizing" the region.

It demonstrates that North Korea "continues to prioritize its weapons of mass destruction and ballistic missile programs over the well-being of its people," White House spokeswoman Jen Psaki said.

The missile was fired on Thursday afternoon from Sunan -- likely the same site as a failed test last week -- and had a range of 6,200 kilometres (3,850 miles), Seoul's Joint Chiefs of Staff said.

Japanese authorities said it appeared to be a "new type" of ICBM that flew for 71 minutes and landed in Japan's territorial waters.

"This is such an outrageous, unforgivable act," Japan's Prime Minister Fumio Kishida said in Brussels where he was meeting with members of the Group of Seven.

North Korea was threatening "peace and safety" for Japan and the region, he said, adding: "This cannot be accepted."

A White House official later said Kishida met with US President Joe Biden on the G7 sidelines to discuss the launch, with Biden conveying Washington's "rock-solid commitment to the security of Japan and the Republic of Korea."

US Defense Secretary Lloyd Austin spoke by phone with his South Korean counterpart Suh Wook.

According to a Pentagon statement, they agreed that "firm responses, including further actions from the UN Security Council, are necessary."

The US, Britain and France have called for an emergency UN Security Council meeting over the launch to be held Friday, diplomats told AFP.

- Hwasong-17 -

The North has carried out three ICBM tests, the last in November 2017, of a Hwasong-15 -- deemed powerful enough to reach the continental United States.

It has long coveted an ICBM that can carry multiple warheads and, Seoul and Washington say, has been testing the Hwasong-17, a giant ICBM first unveiled in October 2020.

Despite biting international sanctions Pyongyang has doubled down on Kim's drive to modernise the military, while ignoring US offers of talks.

From hypersonic to medium-range ballistic missiles, Pyongyang has tested a raft of banned weaponry in 2022, including two recent launches it claimed were of a "reconnaissance satellite".

Washington and Seoul said these tests were actually of components of the Hwasong-17 -- and warned Pyongyang was preparing to test-fire an ICBM at full range.

A launch last week, likely of the Hwasong-17, ended with the missile exploding mid-air above the capital.

"So (Pyongyang) carried out today's launch to make up for that failure and because it has to complete the ICBM technology right away," Go Myong-hyun, senior researcher at the Asan Institute for Policy Studies told AFP.

- Seoul 'disorganised' -

North Korea will mark the 110th anniversary of the birth of founder Kim Il Sung on April 15, and analysts predict Pyongyang will conduct an ICBM or satellite launch as part of the celebrations.

It is also taking advantage of Washington's deteriorating relationships with China and Russia, following Moscow's invasion of Ukraine.

"Kim probably feels this is the perfect time to develop ICBMs while repeatedly reminding the world that the North, unlike Ukraine, is a nuclear-armed country," Ahn Chan-il, a scholar of North Korean studies, told AFP.

South Korea is also going through a presidential transition, with Moon set to hand power to successor Yoon Suk-yeol in May, which creates foreign policy confusion, Hong Min, a researcher at the Korea Institute for National Unification, told AFP.

"For the incoming administration, it is highly likely that they are not yet prepared."