SEOUL (Reuters) - North Korean leader Kim Jong Un supervised a test-fire of a submarine-launched ballistic missile and declared it "the greatest success" that put the country in the "front rank" of nuclear military powers, official media reported on Thursday.

North Korea fired a submarine-launched ballistic missile (SLBM) on Wednesday which flew about 500 km (300 miles). The South Korean government and experts said the launch showed technical progress in the North's SLBM program.

"A test-fire of strategic submarine-launched ballistic missile was successfully conducted under the guidance of supreme commander of the Korean People's Army (KPA) Kim Jong Un," the North's official KCNA news agency said.

"He appreciated the test-fire as the greatest success and victory," KCNA said.

"He noted with pride that the results of the test-fire proved in actuality that the DPRK joined the front rank of the military powers fully equipped with nuclear attack capability."

DPRK is the acronym for the Democratic People's Republic of Korea.

The KCNA report did not give the date of the missile launch as it customarily omits reference to the time and location of the country's leader's activities.

The test showed the solid-fuel missile's control and guidance system as well as the atmospheric re-entry of the warhead all met operational requirements, KCNA said.

The South Korean and U.S. militaries said the missile was fired from near the North's coastal city of Sinpo, where a submarine base is located, toward Japan. Japan said the missile reached its air defense identification zone (ADIZ), the first time by a North Korean missile.

(Reporting by Jack Kim; editing by G Crosse and James Dalgleish)