The U. N. forbids North Korea from conducting missile and nuclear weapons tests and has imposed severe sanctions. However, the East Asian state repeatedly defies the prohibition, and leader Kim Jong-un has promised to strengthen his country's defences. It announced on Friday that it had launched short-range ballistic missiles from train carriages and that it had performed two tests of what it claimed were hypersonic missiles, which are more difficult to detect.

North Korea typically launches missiles to commemorate politically significant occasions in the nation or express its discontent with US-ROK military drills.

Negotiations with the United States, which wants North Korea to give up its nuclear weapons, have stagnated since U.S. President Joe Biden took office. In reaction to some of the previous tests this month, Mr Biden's government placed its first penalties on North Korea last week.