(Bloomberg) -- North Korean leader Kim Jong Un oversaw a nuclear counterstrike drill involving a missile with a mock atomic warhead capable of reaching Japan’s west coast, its official media said.

Kim brought his daughter to exercises over the weekend, where he issued a threat to the US over joint military drills it’s conducting with South Korea, saying his country is preparing to make “an immediate and overwhelming nuclear counterattack anytime,” the Korean Central News Agency reported Monday.

“The missile was tipped with a test warhead simulating a nuclear warhead,” KCNA said. The missile, fitted with detonators and devices to simulate a nuclear attack, exploded at a height of about 800 meters (875 yards) above its target, it said

The test seems to be the first of its type to be mentioned in state media. 

The weekend launch comes after North Korea last week fired an intercontinental ballistic missile designed to carry a nuclear warhead to the US mainland. That test on Thursday came hours before South Korean President Yoon Suk Yeol went to Japan for a summit to repair ties and improve security cooperation.

Kim said that launch was meant to “strike fear into the enemies” of North Korea as joint military exercise were being stepped up.

The latest launches coincided with US-South Korean “Freedom Shield” military drills that started March 13 and run through this week. Pyongyang has denounced the exercises as a prelude to nuclear war and promised an unprecedented response.

Cheon Seong-whun, a former security strategy secretary in South Korea’s presidential office, said North Korea’s latest test was designed to show that it can use missiles for a nuclear attack and could be a prelude for the state’s first test of a nuclear device in the air. All of its six previous nuclear tests have been in tunnels.

“The next step for North Korea would be an exercise with actual nuclear warheads, rather than simulated ones, the actual demonstration-use drill,” Cheon said. “If that happens, North Korea will be able to showcase its nuclear deterrence capabilities to the fullest extent.”

Such a test would likely spread radiation through the atmosphere and cause alarm even among North Korea’s most important partner China, which signed off on UN resolutions in 2017 to punish the state for its tests of long-range missiles and nuclear devices.

North Korea had fired off 13 ballistic missiles since Feb. 18, including two ICBMs and what appeared to be a new close-range ballistic missile designed to hit US bases in South Korea. The tests also included two cruise missiles launched from a submarine — another apparent first.

©2023 Bloomberg L.P.