North Korean leaderKimJongUnsaid his country wouldsoontestanuclearwarheadand ballistic missiles capable of carryingnuclearwarheads, the North's KCNA news agency reported, in what would be a direct violation of U.N. resolutions which have the backing of the North's chief ally, China.
Kimmade the comments as he supervised a successful simulatedtestof atmospheric re-entry of a ballistic missile that measured the "thermodynamic structural stability of newly developed heat-resisting materials", KCNA said.
"Declaring that anuclearwarheadexplosiontestand atest-fire of several kinds of ballistic rockets able to carrynuclearwarheadswillbe conducted in a short time to further enhance the reliance ofnuclearattack capability, he (Kim) instructed the relevant section to make prearrangement for them to the last detail," the agency said.
South Korea's defense ministry said there were no indications of activities at the North'snucleartestsite or its long-range rocket station, but that North Korea continues to maintain readiness to conductnucleartests.
South Korean President Park Geun-hye said the North would lead itself to self-destruction if it did not change and continued the confrontation with the international community.
The North's report comes amid heightened tension on the Korean peninsula as South Korean and U.S. troops stage annual military exercises that Seoul has described as the largest ever.
In the apparent re-entry simulation, the official newspaper of North Korea's ruling Workers' Party carried pictures on Tuesday of a dome-shaped object placedunder what appeared to be a rocket engine and being blasted with flaming exhaust. In separate images,Kimobserved the object described by KCNA as awarheadtip.
The North has issued belligerent statements almost daily since comingunder a new U.N. resolution adopted this month to tighten sanctions against it after anucleartestin January and the launch of a long-range rocket last month.
In 1962, theUnited States launched a ballistic missile with a livewarheadin what was known as the Frigate Birdtest. China conducted a similartestin 1966.
"What would be terrible is if the DPRK (North Korea) re-enacted Operation Frigate Bird or the fourth Chinesenucleartestand did a two-in-one," said Jeffrey Lewis of the California-based Middlebury Institute of International Studies.
"For now, though, it looks like anucleartestand several missiletests in close succession."
South Korea's defense ministry said after the North's report that it still does not believe the North has acquired missile re-entry technology.
U.S. and South Korean experts have said the general consensus is that North Korea has not yet successfully miniaturized anuclearwarheadto be mounted on an intercontinental ballistic missile.
More crucially, the consensus is that there have been notests to prove it has mastered the re-entry technology needed to bring a payload back into the atmosphere.
Kimsaid last week his country had miniaturized anuclearwarhead.
The North, which has conducted fournucleartests, also claims that its Januarynucleartestwas of a hydrogen bomb, although most experts said the blast was too small for it to have been from a full-fledged hydrogen bomb.
The North alsosaysthe satellites it has launched into orbit are functioning successfully, although that has not been verified independently.
North Korea rejects criticism of itsnuclearand missile programs, even from old ally China, saying it has a sovereign right to defend itself from threats and to runa space program putting satellites into orbit.
China's Foreign Ministry on Tuesday urged prudence.
"We urge all the relevant sides to conscientiously carry out what is required by the U.N. Security Council, speak and act cautiously, and all relevant sides must not take any action that would exacerbate tensions on the Korean peninsula," said ministry spokesman Lu Kang at a regular briefing.
The new U.N. Security Council resolution sharply expanded existing sanctions by requiring member states to inspect all cargo to and from North Korea and banning the North's trade of coal when it is seen as funding its arms program.
The foreign ministers of South Korea and China discussed the new sanctions against North Korea by telephone late on Monday and agreed it was important to implement them "in a complete and comprehensive manner", China said on Tuesday.