South Korea test-fired its first homegrown hypersonic weapon on Thursday, the presidential office said, days after Pyongyang said it had launched an intermediate-range hypersonic missile.

"President Lee Jae Myung observed the first test launch of a hypersonic glide vehicle (HGV) -- currently under research and development using domestic technology -- this afternoon," the presidential Blue House said in a statement.

The weapon system is a "key strategic asset capable of changing the course of the battlefield", it added, and the warheads' "unpredictable flight trajectories and overwhelming speed enable them to strike key strategic targets."

Hypersonic glide vehicles are sent into the upper atmosphere via rocket boosters, then glide towards their target at five times the speed of sound or greater.

Seoul's announcement came days after North Korea claimed it had tested an intermediate-range hypersonic missile.

Pyongyang has said that the Saturday launch involved the use of AI, which it said meant there was "no way to avoid" the missile's attack.

Pyongyang has also said its missile was "capable of changing its flight orbit at a low altitude".

Seoul and Washington have also said the North Korean missile was "at a level that can be sufficiently detected and intercepted using the defensive assets possessed by the two allies."