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 doomed diplomacy, which collapsed in 2019.

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

"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 violation of Security Council regulations that "needlessly raises tensions and risks destabilizing the security situation in the region".

"This action demonstrates that the DPRK 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 in a statement, referring to North Korea's official name, the Democratic People's Republic of Korea.

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 "the peace and safety of Japan, the region and the international community," he added.

"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."

In a phone call late Thursday, Japan's foreign secretary Yoshimasa Hayashi and US Secretary of State Antony Blinken "strongly condemned" the launch, according Tokyo.

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 over its weapons programmes, 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".

The United States and South Korea said this month 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 in failure, with the missile exploding mid-air in the skies 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.

"Kim Jong Un feels it's very important to prove his leadership's competency before the 110th birthday anniversary of Kim Il Sung," said Cheong Seong-chang of the Center for North Korea Studies at the Sejong Institute.

North Korea 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.

"Everything is very disorganised and all over the place," he said.

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