This photo released on Monday by North Korea's state media shows what Pyongyang claims is a solid-fuel hypersonic intermediate-range ballistic missile being launched from an undisclosed location in the North the previous day. Yonhap

North Korea said on Monday it successfully test-fired a new solid-fuel missile tipped with a hypersonic maneuverable warhead, marking the latest breakthrough that analysts said poses a significant threat to South Korea's air defense system.

The launch, North Korea's first known weapons test this year and the first-ever of a solid-fuel hypersonic intermediate-range ballistic missile (IRBM), was aimed at checking the reliability of new solid-fuel engines and the maneuverable flight capabilities of the warhead, according to the North's official Korean Central News Agency. It added that the test was a success.

The announcement came just days after North Korean leader Kim Jong-un threatened to "annihilate" South Korea and the United States, its key ally, if they attempt to challenge Pyongyang's sovereignty by force.

South Korea's military said the missile, fired from or near Pyongyang, flew about 1,000 kilometers before falling into the waters off its east coast. North Korea did not elaborate on the results. But a typical IRBM is capable of traveling 3,000-5,500 kilometers. This means one fired from the North could reach anywhere in the South as well as U.S. military bases in Guam or Japan at five times the speed of sound. If the claim is true, a hypersonic missile fired from the North Korean capital could strike a target in Seoul in just about a minute.

The latest launch has sent alarm bells ringing in South Korea as there is currently no system in place to intercept such missiles, according to experts.

"The North Korean missile presents two challenges for South Korea's military. First, missiles that use solid fuel are easier to transport and faster to fire than liquid-fuel ones. As a result, early detection and, therefore, preemptive strike would be difficult," said Kim Yeoul-soo, an analyst at the Korea Institute for Military Affairs, a think tank. "Also, hypersonic missiles are extremely difficult to intercept given their high speed, maneuverability, low flight paths and unpredictable trajectories. Currently, neither South Korea nor the U.S. military has any reliable defense system against such threats."

Hypersonic missiles were among the advanced weapons the North Korean leader vowed to develop. Hypersonic missiles test-fired in 2022 and 2023 were liquid-fuel types that traveled up to 10 times the speed of sound. Analysts said North Korea appears to have been increasingly shifting to solid-fuel missiles with the aim of undermining ― and ultimately incapacitating ― South Korea and the U.S.' capability to detect and defend against missile threats.

"It appears to be North Korea's solution to our Kill Chain (preemptive strike system) and air defense under development," said Shin Jong-woo, a senior analyst at the Korea Defense Security Forum, a think tank.

South Korea is developing long-range surface-to-air missiles to improve its air defense against hypersonic weapons. If everything goes as planned, the new missiles are expected to be deployed as early as 2028.

The Ministry of National Defense condemned the latest provocation from the North, saying it was a clear violation U.N. Security Council resolutions, while warning that an attack on South Korea would be met with an "overwhelming response."

On the same day, North Korean Foreign Minister Choe Son-hui arrived in Moscow for talks with her Russian counterpart Sergei Lavrov as the two countries deepen ties in security and other sectors.

Some experts have expressed concerns that Russia, known for advanced hypersonic missile technology, might support North Korea in developing its version of the Avangard, a nuclear-capable, hypersonic boost-glide vehicle developed by Russian scientists.