“Pyongyang’s show of force should be of concern beyond Seoul, as its military cooperation with Moscow adds to the violence in Ukraine, and because it may be more willing to challenge the US and its allies while global attention is fixed on the Middle East,” Easley warned.

Choe’s visit, which followed Lavrov’s trip to Pyongyang in October, also comes amid allegations that the North provided weapons to Russia for its war with Ukraine in return for Moscow’s technical assistance for Pyongyang’s weapons programme.

Both Pyongyang and Moscow have denied any arms deals.

The missile loaded with a hypersonic warhead was launched on Sunday in a test aimed at verifying the warhead’s gliding and manoeuvring capabilities and the reliability of newly developed multi-stage high-thrust solid-fuel engines, the North’s Korean Central News Agency (KCNA) said.

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Kim Jong-un vows to accelerate war preparations, while the South holds rare defence drills

Kim Jong-un vows to accelerate war preparations, while the South holds rare defence drills

News reports earlier said South Korean and Japanese authorities were apparently having difficulties in verifying its altitude and flight course, raising the possibility that it might be a course-altering, low-flying hypersonic missile.

Because of their speed and manoeuvrability, such missiles would pose a challenge to regional missile defence systems, analysts said.

“This missile appears to have a manoeuvrable re-entry vehicle that is capable of changing its trajectory, making it difficult to track and intercept,” Lee Il-woo, an analyst at the thin tank Korea Defence Network, told This Week in Asia.

This could not only neutralise South Korea’s missile defence system but pose a serious threat to US strategic assets such as its aircraft-carrier striker groups operating in the West Pacific, he cautioned.

“These kinds of missiles could also be used to help China by deterring US aircraft carriers from approaching the South China Sea if things go awry in the Taiwan Strait,” he said. “This is another step forward for the North in its efforts to build up its military might.”

The North’s Missile General Bureau stressed the test-fire “never affected the security of any neighbouring country and had nothing to do with the regional situation”, and said the test was part of the country’s “regular activities for developing powerful weapon systems”, according to the KCNA.

The launch came two months after North Korea said it successfully tested engines for a new solid-fuel IRBM, which reflected a push to advance its line-up of weapons targeting US military bases in Guam and Japan.

Chang Young-keun, a missile expert at South Korea’s Research Institute for National Strategy, said the Sunday test would have been focused more on developing a solid-fuel first stage for an IRBM than evaluating the purported hypersonic warhead.

Experts say it was unclear if the North’s hypersonic vehicles consistently maintained a desired speed exceeding Mach 5 during tests in 2021 and 2022.

But it is likely that the North is trying to build a hypersonic weapons system powered by solid-fuel booster rockets, simultaneously with its efforts to develop the new IRBM, and it may conduct more flight tests soon, according to Chang.

“In particular, a hypersonic missile with IRBM-level range would be an effective means for evading US missile defences and striking Guam,” Chang said about the North’s ambitions.

The North last year tested its first solid-fuel intercontinental ballistic missile, adding to its arsenal of weapons targeting the US mainland. It also launched its first military reconnaissance satellite in November, vowing to fire more.

At a year-end party meeting, North Korean leader Kim urged stepped-up war preparations to cope with what he called “unprecedented” acts of US-led confrontation against his country.

Last week, Kim called South Korea the country’s “principal enemy” and said he had “no intention of avoiding war”.

Kim also threatened to annihilate the South if it attempted to use force against the North, according to KCNA.

Kim warns North Korea won’t hesitate to wipe out ‘principal enemy’ Seoul

Experts said North Korea was likely to ratchet up tensions ahead of the South’s parliamentary polls in April and the US presidential election in November.

Yang suggested Pyongyang intended to signal to other countries that it was only implementing an already announced arms build-up programme.

“Tensions are expected to mount during the annual US-South Korea joint military exercises scheduled in March and August and in the lead-up to the parliamentary elections in April in the South and the US presidential election in November”, he added.

Additional reporting by Associated Press