N.K. says it tested underwater nuclear weapons system in response to trilateral drills

North Korea said Friday it has tested an underwater nuclear weapons system under development in response to the latest joint maritime exercise involving South Korea, the United States and Japan.

North Korea’s defense ministry said the country conducted an important test of the Haeil-5-23 in the East Sea, denouncing this week’s naval drills involving a U.S. nuclear aircraft carrier as “reckless confrontation hysteria,” according to the Korean Central News Agency (KCNA).

The KCNA did not disclose details, including the weapons’s specifications and the test date.

“Our army’s underwater nuke-based countering posture is being further rounded off, and its various maritime and underwater responsive actions will continue to deter the hostile military maneuvers of the navies of the U.S. and its allies,” a spokesman of the North’s defense ministry said in a statement carried by the KCNA.

The official condemned the three nations for “seriously threatening the security” of North Korea and sternly warned of “catastrophic consequences” for their acts, the report said.

In response, South Korea denounced the North’s claimed weapons test as a violation of United Nations Security Council resolutions and a provocative act that threatens peace on the Korean Peninsula and around the world.

“Under a robust South Korea-U.S. combined defense posture, our military has maintained a thorough readiness posture against North Korea’s provocations and will respond overwhelmingly if the North stages a direct provocation against South Korea,” the defense ministry said in a statement.

South Korea, the U.S. and Japan jointly conducted naval drills involving the USS Carl Vinson nuclear-powered aircraft carrier from Monday to Wednesday, following Pyongyang’s latest launch of a hypersonic missile.

Pyongyang has long denounced joint military drills between Seoul and Washington as a rehearsal for an invasion.

In March last year, North Korea first made public a test of its underwater attack drone, the Haeil-1, claiming the “secret weapon” is capable of generating a “radioactive tsunami” and stealthily attacking enemies. In April, the country carried out a test of the Haeil-2 attack drone.

At a year-end party meeting, North Korean leader Kim Jong-un called for stepped-up war preparedness to deter what he called “unprecedented” acts of U.S.-led confrontations. Kim also defined inter-Korean ties as relations between “two states hostile to each other.”