North Korea said it has tested a new solid-fuel missile fitted with a hypersonic warhead as it continued efforts to develop more powerful, harder-to-detect weaponry.

The launch took place on Sunday afternoon and came as Foreign Minister Choe Son Hui headed to Moscow amid concerns in the United States and elsewhere that Pyongyang was selling weapons to Russia for use in Ukraine in return for Russian technological expertise.

Detected by neighbouring Japan and South Korea, the launch was designed to test the reliability of new multi-stage, high-thrust solid-fuel engines and an intermediate-range hypersonic manoeuvrable controlled warhead, the state-run Korean Central News Agency (KCNA) reported on Monday.

KCNA added that the test-firing “never affected the security of any neighbouring country and had nothing to do with the regional situation”.

The missile flew towards the East Sea, travelling approximately 1,000km (621 miles), Seoul’s Joint Chiefs of Staff said in a statement on Sunday, adding that authorities in Seoul, Washington, DC and Tokyo were analysing the specifications. Japan’s Defence Ministry said its maximum altitude was at least 50km (30 miles).

North Korea’s last missile test was of a Hwasong-18 solid-fuel intercontinental ballistic missile (ICBM), which it fired into the East Sea on December 18.

It previously tested new solid-fuel engines for an intermediate ballistic missile on November 11 and November 14.

Leader Kim Jong Un last week branded Seoul his “principal enemy” and warned he would not hesitate to annihilate South Korea.

“The historic time has come at last when we should define as a state most hostile toward the Democratic People’s Republic of Korea the entity called the Republic of Korea [South Korea],” Kim was reported as saying by KCNA.