North Korea said Wednesday that it had already entered a technical level of “miniaturizing and diversifying” nuclear capabilities, further escalating security threats that were heightened by its recent underwater test of a submarine-launched ballistic missile.

Experts said that Pyongyang’s verbal threat appeared to represent its growing frustration over its isolation and the international community’s refusal to recognize its evolving nuclear capabilities including its SLBM technology, which some experts discounted as a “bluff.”

“We have entered a (technical) phase of miniaturizing and diversifying our nuclear strike means. Don’t dare to challenge our measures to strengthen our legitimate self-defense capabilities,” the policy division of the powerful National Defense Commission said in a statement.

“It has already been long since we entered the phase. We are also at a stage to secure the top-level striking accuracy of our long-range rockets as well as short- and mid-range rockets,” it added.

The statement also portrayed its recent underwater test of the SLBM as a “great feat” and a culmination of North Korea’s efforts to bolster its military might, claiming that “the world acclaimed and praised the test with surprise and envy.”

Pyongyang ratcheted up tensions earlier this month by claiming that it succeeded in conducting an underwater test of the SLBM. The claim over the test has caused security concerns in the South, as it has almost no way to cope with the SLBM threat.

Koh Yoo-hwan, North Korea expert at Dongguk University, said that the North’s claim over the enhanced nuclear capability seems to reflect its frustration over the situation in which there are no international efforts to negotiate with the nuclear-ambitious regime.

“Now there are no talks whatsoever over North Korea’s nuclear program. And there are only sanctions and isolation. Thus, by forging a sense of a crisis, the North appears to ask (the international community) whether it would begin talks with North Korea or not,” he said.

“It appears that the North is also frustrated by the fact that tension with the South is still ongoing even after the end of the South Korea-U.S. military drills.”

By Song Sang-ho (sshluck@heraldcorp.com)