Leader Kim Jong Un says North Korea has achieved the "success of all successes" with a submarine-launched missile test.
Kim says in a statement Thursday that the test arms the country with fully-equipped nuclear attack capability and puts the U.S. mainland within its striking distance.
Kim's statement was carried by Pyongyang's official Korean Central News Agency. It came a day after South Korean officials said they detected a ballistic missile fired from a North Korean submarine that flew about 500 kilometers (310 miles), the longest distance achieved by the North for such a weapon.
North Korea already has land-based missiles that can hit South Korea and Japan, including U.S. military bases in those countries. Reliable submarine-launched missiles would add weapons that are harder to detect.