North Korea says it tested a new multiwarhead missile. South Korea says it's covering up a failure

North Korea said Thursday it had successfully tested a multiwarhead missile in the first known launch of a developmental weapon coveted by leader Kim Jong Un to overwhelm US and South Korean missile defences. South Korea quickly dismissed the claim as deception to cover up a failed launch.

North Korea's state media said the launch Wednesday tested the separation and guidance control of individual mobile warheads to ensure the capability of the Multiple Independent Reentry Vehicles.

It said the separated warheads "were guided correctly to the three coordinate targets" and a decoy that separated from the missile was verified by radar.

If confirmed, it would be North Korea's first public launch event related to the development of a multiwarhead missile, though at a preliminary stage.

South Korea's military said later Thursday that a joint analysis by South Korean and US authorities assessed that the North Korean missile launch failed.

Joint Chiefs of Staff spokesperson Lee Sung Joon told reporters that the separation of warheads in MIRV tests happens in descending stages but the North Korean missile exploded in the initial stage of its flight.

He said North Korean photos of the launch showed a weapon similar to a liquid-fuel Hwasong-17 ICBM that the country test-fired in March 2023.

The South Korean military's earlier assessment Wednesday was that a suspected solid-fuelled hypersonic missile was launched and exploded off the North's east coast, scattering fragments in the water.

It said it detected more smoke than normal launches, suggesting a possible combustion issue caused by an engine fault.

A multiwarhead missile was among the high-tech weapons systems Kim cited on his wish list during a ruling party meeting in early 2021, along with spy satellites, solid-fuel intercontinental ballistic missiles, hypersonic weapons and submarine-launched nuclear missiles.

North Korea has since performed a series of tests to develop such weapons systems.

"I had been anticipating a MIRV test for some time now, as this was one of the last remaining items on Kim Jong Un's modernisation wish list from the 8th Party Congress back in January 2021," said Ankit Panda, a senior analyst at the Carnegie Endowment for International Peace.

Panda said Wednesday's test appeared to be an initial evaluation of some of the key subsystems to develop a workable MIRV.

He expects successive tests of the technology to follow, leading up to a launch of an intercontinental ballistic missile on a lofted trajectory. Panda said it appeared that "South Korea misinterpreted the nature of this test initially."

Lee Choon Geun, an honorary research fellow at South Korea's Science and Technology Policy Institute, said North Korea appeared to have begun testing individual technological elements of multiwarhead missiles. He said more tests are expected to perfect the separation and guidance control and other facets of multiwarhead missile technology.

Chang Young-keun, a missile expert at Seoul's Korea Research Institute for National Strategy, said the North Korean test hasn't yet proved it has sufficient MIRV controlling technologies needed for ICBMs. He said North Korea didn't release enough information to verify its MIRVs made successful atmospheric reentries and hit designated targets.

Panda said the the presence of a decoy in the North Korean test is significant. But South Korea's military said it couldn't immediately confirm whether North Korea has the technology to build such a decoy.

"North Korea has made no secret of its intention to stress and overcome US homeland missile defences," Panda said. "Decoys will assist in that endeavour and will likely be incorporated onto their single-warhead missiles as well."

The North Korean test, its first weapons display in a month, came as the country protests the regional deployment of a US aircraft carrier for a joint training with South Korea and Japan. North Korean Vice Defence Minister Kim Kang Il on Monday called the carrier's deployment "reckless" and threatened unspecified responses.

In recent weeks, North Korea has also floated numerous trash-carrying balloons toward South Korea in what it has described as a tit-for-tat response to South Korean activists sending political leaflets via their own balloons.

In response, South Korea on June 9 briefly conducted propaganda loudspeaker broadcasts at border areas for the first time in years.

South Korea Thursday said it'll turn on loudspeakers again if North Korea keeps sending trash balloons.

Worries about North Korea also deepened last week when Kim Jong Un and Russian President Vladimir Putin signed a deal requiring each country to provide aid to the other if it is attacked and vowed to boost other cooperation. Analysts say the accord represents the strongest connection between the two countries since the end of the Cold War.

Lee, the expert, said how soon North Korea can complete the development of a multiwarhead weapon depends on whether and how much technology support Russian provides to North Korea. South Korea's military said a Russian assistance to the North Korean MIRV programs hasn't been confirmed.