North Korea test-fired a newly developed hypersonic missile on Tuesday as part of efforts to achieve its five-year weapons development plan, state-run media said, fanning worries that it has improved technology on the hard-to-intercept projectile.

The official Korean Central News Agency's report came on Wednesday, a day after the Japanese government said North Korea fired what appeared to be a ballistic missile in the second such launch in two weeks, with the projectile believed to have splashed into waters outside of Japan's exclusive economic zone in the Sea of Japan.

"The stability of the engine as well as of (a) missile fuel ampoule that has been introduced for the first time" was confirmed, the news agency said. It did not mention whether North Korean leader Kim Jong Un watched the test-firing.

Photo shows a hypersonic missile being test-fired by North Korea on Sept. 28, 2021. (KCNA/Kyodo)

The fuel "ampoule" seems to be referring to a container of liquid fuel, which reduces the preparation time for a missile launch and makes the weapon ready for use almost as fast as a solid-fuel missile, South Korea's Yonhap News Agency said.

KCNA said the development of the Hwasong-8 hypersonic missile "has been pushed forward according to a sequential, scientific and reliable development process," adding, "The test results proved that all the technical specifications met the design requirements."

U.N. Security Council resolutions ban North Korea from launching ballistic missiles.

A hypersonic missile can basically travel at more than five times the speed of sound. Given it is difficult for existing missile defense systems to intercept such a projectile, fears about regional security would grow if North Korea has obtained such capabilities, military experts say.

Yonhap said Tuesday that North Korea's missile flew less than 200 kilometers and reached an altitude of about 30 km.

At a ruling party meeting in January, North Korea pledged to introduce a "hypersonic gliding flight warhead."

Pak Jong Chon, a close aide to Kim, observed Tuesday's missile test, the news agency said. He was reportedly promoted to the Politburo of the Central Committee of the Workers' Party of Korea earlier this month.

The U.S. State Department said in a statement, "We are working to confirm the specific nature of the recent launch event and consulting closely with our allies."

"We take reports of any new capability seriously, and as we've said, we condemn any illicit missile launches, which are destabilizing to the region and to the international community," the department added.

Japanese Chief Cabinet Secretary Katsunobu Kato said at a regular press conference on Wednesday, "We will continue to carefully monitor North Korea's military development in close cooperation with the United States and others."

North Korea's latest missile test came on the same day the nation convened a session of its top legislature, the Supreme People's Assembly.

At the gathering, issues such as city development, education of young people and amendment of the national economic plan were discussed, KCNA reported.

While the country's economy has been languishing amid the coronavirus pandemic, and negotiations with the United States on denuclearization and sanctions relief have stalled, North Korea has repeatedly test-fired missiles.

On Sept. 13, state-run media said the nation had carried out tests of a new long-range cruise missile. Two days later, North Korea fired two ballistic missiles into waters within Japan's exclusive economic zone in the first test of such weapons in nearly six months.

Just days earlier, meanwhile, Kim Yo Jong, the influential younger sister of Kim, left the door open for an inter-Korean summit, while criticizing what she called an "arms buildup" by the United States and South Korea.

North Korea has faced the worst food crisis in over a decade, raising concern that its citizens may be struggling to even receive daily necessities.

Under the circumstances, Kim Jong Un is thought to want the United States to ease economic sanctions that have been imposed to thwart Pyongyang's ballistic missile and nuclear ambitions.

The United States and North Korea remain technically in a state of war as the 1950-1953 Korean War -- in which U.S.-led U.N. forces fought alongside the South against the North, backed by China and the Soviet Union -- ended in a cease-fire, not a peace treaty.

Washington and Pyongyang have no diplomatic relations.

Related coverage:

North Korea fires what appears to be ballistic missile

North Korean leader Kim's sister eager to improve inter-Korean ties

North Korea will reject proposal from South to declare Korean War over