North Korea conducted what is thought to be its largest intercontinental ballistic missile (ICBM) test ever on Thursday, the South Korean and Japanese militaries said, marking a dramatic end to a self-imposed moratorium on long-range testing.

    It would be the first full-capability launch of the nuclear-armed state's largest missiles since 2017, and represents a major step in the North's development of weapons that might be able to deliver nuclear warheads anywhere in the United States.

    U.S. Secretary of State Antony Blinken, who was in Brussels where Biden met with fellow Western leaders in a show of unity against the Kremlin's war in Ukraine, spoke by phone with counterparts in Japan and South Korea after the launch.

    Japanese Foreign Minister Yoshimasa Hayashi said they had agreed that North Korea's move represented a clear and grave challenge to the international community.

    Thursday's launch would be at least the 11th North Korean missile test this year, an unprecedented frequency.

Japanese authorities said the launch appeared to be a "new type" of ICBM that flew for about 71 minutes to an altitude of about 6,000km (3,728 miles) and a range of 1,100 km (684 miles) from its launch site.

    It landed inside Japan's exclusive economic zone (EEZ), 170 km (106 miles) west of the northern prefecture of Aomori, at 3:44 p.m. (0644 GMT), the coast guard said.

    South Korea's Joint Chiefs of Staff put the missile's maximum altitude at 6,200 km and its range at 1,080 km.

That is further and longer than North Korea's last ICBM test in 2017, when it launched a Hwasong-15 missile that flew for 53 minutes to an altitude of about 4,475 km and range of 950 km.

    U.S. and South Korean officials have warned recently that North Korea had been preparing to test-fire its largest ICBM yet, the Hwasong-17. U.S. officials said two recent tests featured the Hwasong-17 system, but did not demonstrate full ICBM range or capability.

    South Korean officials were also examining whether North Korea on Thursday might have launched its previously tested Hwasong-15, possibly with its rocket thrusters and warhead weight adjusted to increase flight time, Yonhap news agency reported, citing unnamed sources.

    Amid a flurry of diplomacy in 2018, Kim declared a self-imposed moratorium on testing ICBMs and nuclear weapons, but later suggested the North could resume such testing amid stalled denuclearisation talks.

    That moratorium had often been touted as a success by former U.S. President Donald Trump, who held historic summits with Kim in 2018 and 2019, but never gained a concrete pact to limit the North's nuclear or missile arsenals.

    New construction has also been spotted at North Korea's only known nuclear test site, which was shuttered in 2018.

    The looming prospect of possible nuclear tests, more joint U.S.-South Korea military drills, and the new conservative South Korean president mean "all conditions are present for a tit-for-tat chain reaction of escalatory steps", said Chad O'Carroll, CEO of Korea Risk Group, which monitors North Korea.

    "Though Biden would prefer to focus exclusively on the Ukraine crisis, it's likely he will soon face crisis-level tensions between the Koreas," he said.