North Korea confirmed Friday that it tested this week a submarine capable of launching a nuclear attack that could “cause a large-scale radiation tsunami” via an underwater explosion, while blaming deteriorating regional security on joint U.S. and South Korea military exercises.

North Korea's official news agency reported Friday that the North Korean military deployed and tested during Tuesday-Thursday exercises off South Hamgyong province with the mission of "causing a large-scale radiation tsunami" via an underwater explosion to destroy hostile ships and ports.

It noted that this submarine “can be deployed on any coast or port and towed by a surface vessel.”

The “secret weapon” was placed Tuesday in the waters off southern Hamgyong province and dawn Thursday with an experimental warhead, the agency said.

North Korean leader Kim Jong Un “directed” the drills and said they should serve as a warning to the United States and South Korea in order to “recognise the DPRK’s unlimited ability to deter...”, using North Korea’s official name.

Kim “expressed his desire to make the American imperialists and the puppet regime in South Korea sink into despair,” the agency said.

North Korea fired several cruise missiles Wednesday, according to the South Korean military, which is currently conducting large-scale joint exercises with the United States.

However, analysts questioned North Korea’s assertions.

Professor Leif-Eric Easley of Iowa University in Seoul said the idea of having Pyongyang “a march capable of carrying nuclear weapons must be met with questioning.”

“Pyongyang’s assurances about a new weapons system are different from a credible demonstration of its capabilities,” he added.

In a tweet, U.S. analyst Ankit Banda did not rule out that the test was a “psychological attempt at deception/operation.”

But after all, these assertions are “shocking,” Xiongseong-chang of the Sejong Institute told AFP.

If true, it would be hard to know how Seoul would respond “to such a new North Korean weapon that (as you say) could completely destroy the main ports operating in the south.”

North Korea’s official news agency also said that “Pyongyang is more than willing to use its tactical nuclear weapons at any time,” the researcher said Chan-il told AFP.

- Nuclear power? -

After a year that saw a record number of weapons tests and growing nuclear threats from Pyongyang, Seoul and Washington boosted defense cooperation and conducted the largest joint military exercises in five years from March 13 to 23, 2023.

North Korea views the drills as invasion drills on its territory and has repeatedly warned it will take “overwhelming” measures in response.

The North Korean news agency on Friday described the joint U.S.-South Korea drills dubbed Freedom Shield as a maneuver aimed at “occupying” North Korea.

Pyongyang’s “underwater nuclear attack” drills were “with the aim of warning the enemy of a real nuclear crisis,” the agency said.