North Korea announced Thursday that its missile test the previous day involved a new type of submarine-launched ballistic missile (SLBM).
Pyongyang's state-run KCNA news agency claimed the successful launch "ushered in a new phase in containing the outside forces' threat."
"The test-firing scientifically and technically confirmed the key tactical and technical indexes of the newly-designed ballistic missile," KCNA added.
This was the North's 11th missile test of the year but its first SLBM test since 2016, and the reclusive state is barred from developing ballistic missile technology under United Nations Security Council restrictions.
U.S. President Donald Trump openly tolerated previous tests on the basis that they were short-range launches, but he is yet to comment on North Korea experimenting with a potentially far more threatening SLBM.
Officials from Washington and Pyongyang are due to hold working-level negotiations over the North's denuclearization this Saturday.
By Alex Jensen in Seoul