North Korea says its latest weapons test was of a submarine-launched ballistic missile that marked a "new phase" in its defence capability, just days before the resumption of stalled nuclear talks with the US.
The test was by far the most provocative since Pyongyang first began a dialogue with Washington in 2018, and marked a significant step in North Korea's nuclear weapons programme, analysts said.
A proven submarine-based missile capability would take the North's arsenal to a new level, allowing deployment far beyond the Korean peninsula and a second-strike capability in the event of an attack on its military bases.
"The new-type ballistic missile was fired in vertical mode" on Wednesday in the waters off Wonsan Bay, the Korean Central News Agency (KCNA) reported, identifying the weapon as a Pukguksong-3.
"The successful new-type SLBM test-firing comes to be of great significance as it ushered in a new phase in containing the outside forces' threat," it added.
The North's leader Kim Jong Un sent "warm congratulations" to research units involved in the launch.
Kim has personally supervised recent land-based missile tests.
Photos carried by the official Rodong Sinmun newspaper showed a black and white missile emerging from the water and appearing to shoot into the sky.
The images also showed a small towing vessel next to the missile, which analysts said indicates the test was conducted from a submersible barge rather than an actual submarine, and that the system was in its early stages.
Ankit Panda of the Federation of American Scientists called it Pyongyang's longest-range-capable solid-fuel missile, adding Wednesday's launch was "unambiguously the first nuclear-capable missile test since November 2017".
"Kim Jong Un's 'rocket men' kept busy during the diplomatic charm offensives of 2018-2019," said Panda.
The North carried out a successful test of the solid-fuel Pukguksong-1, also known as KN-11, in August 2016, which flew around 500 kilometres.
In July, North Korean state media had published pictures of Kim Jong Un inspecting a new type of submarine that also showed a poster of the Pukguksong-3 on a wall, fuelling concerns that Pyongyang was pushing ahead with an SLBM programme.
Tokyo said a part of Wednesday's missile landed in waters within Japan's exclusive economic zone -- a 200-kilometre band around Japanese territory.
Washington voiced alarm, with a State Department spokesperson calling on Pyongyang "to refrain from provocations" and "remain engaged in substantive and sustained negotiations" aimed at bringing stability and denuclearisation.
North Korea is banned from ballistic missile launches by United Nations Security Council resolutions.
The launch came ahead of planned resumption of working-level talks between Pyongyang and Washington which is slated for later this week in an undisclosed location.
North Korea frequently couples diplomatic overtures with military moves as a way of maintaining pressure on negotiating partners, analysts say, and may believe this weapons system gives it added leverage.
Pyongyang tested what it called a "super-large" rocket launcher last month just hours after the North said was willing to resume working-level talks with Washington.
Kim Dong-yub, a researcher at the Institute for Far Eastern Studies, noted Kim's absence at Wednesday's launch -- a rarity as the North Korean leader has been present at all recent weapons tests.
"It's likely not unrelated to the talks between Pyongyang and Washington currently under way," he said, adding that Kim was trying to carry out weapons modernisation without jeopardising dialogue with the US.
Negotiations have been deadlocked since a second summit between Kim and US President Donald Trump in February ended without a deal.
The two agreed to restart dialogue during an impromptu meeting at the Demilitarised Zone dividing the two Koreas in June, but those talks have yet to materialise.
Pyongyang also carried out several weapons tests since the meeting that have been downplayed by Trump, who dismissed them as "small" and insisted his personal ties with Kim remained good.