SEOUL (AFP) - North Korean leader Kim Jong Un has declared a recent submarine-launched ballistic missile (SLBM) test the "greatest success", Pyongyang's state media said on Thursday (Aug 25).

The results of Wednesday's launch proved the North had joined the "front rank of the military powers fully equipped with nuclear attack capability" and that the United States mainland and the operational theatre in the Pacific were now "within the striking range" of the North's army, KCNA news agency reported Mr Kim as saying.

The missile flew 500km towards Japan, marking what weapons analysts called a clear step forward for North Korea's nuclear strike ambitions.

Mr Kim stressed the need for stepped-up efforts to mount nuclear warheads on ballistic missiles and to develop means to deliver them in order "to cope with the unpredicted total war and nuclear war with the US imperialists", KCNA said.

"I do not guess what ridiculous remarks the US and its followers will make about this test-fire, but I can say their rash acts will only precipitate their self-destruction," Mr Kim was quoted as saying by KCNA.

A proven SLBM system would take North Korea's nuclear strike threat to a new level, allowing deployment far beyond the Korean peninsula and a "second-strike" capability in the event of an attack on its military bases.

South Korea's Joint Chiefs of Staff said in a statement following the launch that the North was clearly bent on escalating tensions and said the SLBM test posed a "serious challenge" to security on the Korean peninsula.

"We will deal strongly and sternly with any provocation by the North," it said.

Current UN resolutions prohibit North Korea from any use of ballistic missile technology, but Pyongyang has continued to carry out numerous launches following its fourth nuclear test in January.