SEOUL, South Korea (AP) — North Korea’s recent barrage of missile launches were the simulated use of its tactical battlefield nuclear weapons to “hit and wipe out” potential South Korean and U.S. targets, state media reported Monday, as its leader Kim Jong Un signaled he would conduct more provocative tests.

The North’s statement, released on the 77th birthday of its ruling Workers’ Party, is seen as an attempt to burnish Kim’s image as a strong leader at home amid pandemic-related hardships as he’s defiantly pushing to enlarge his weapons arsenal to wrest greater concessions from its rivals in future negotiations.

“Through seven times of launching drills of the tactical nuclear operation units, the actual war capabilities … of the nuclear combat forces ready to hit and wipe out the set objects at any location and any time were displayed to the full,” the North’s official Korean Central News Agency said.

KCNA said the missile tests were in response to recent naval drills between U.S. and South Korean forces, which involved the nuclear-powered aircraft carrier USS Ronald Reagan for the first time in five years.

Viewing the drills as a military threat, North Korea decided to stage “the simulation of an actual war” to check and improve its war deterrence and send a warning to its enemies, KCNA said.

North Korea considers U.S.-South Korean military drills as an invasion rehearsal, though the allies have steadfastly said they are defensive in nature. Since the May inauguration of a conservative government in Seoul, the U.S. and South Korean militaries have been expanding their exercises, posing a greater security threat to Kim.

The launches — all supervised by Kim — included a nuclear-capable ballistic missile launched under a reservoir in the northeast; other ballistic missiles designed to launch nuclear strikes on South Korean airfields, ports and command facilities; and a new-type ground-to-ground ballistic missile that flew over Japan, KCNA reported. It said North Korea also flew 150 warplanes for separate live-firing and other drills in the country’s first-ever such training.

Cheong Seong-Chang at the private Sejong Institute in South Korea said the missile launches marked the first time for North Korea to perform drills involving army units tasked with the operation of tactical nuclear weapons.

The North’s public launch of a missile from under an inland reservoir was also the first of its kind, though it has previously test-launched missiles from a submarine.

Kim Dong-yub, a professor at Seoul’s University of North Korean Studies, said North Korea likely aims to diversify launch sites to make it difficult for its enemies to detect its missile liftoffs in advance and conduct preemptive strikes.

KCNA said when the weapon launched from the reservoir was flying above the sea target, North Korean authorities confirmed the reliability of the explosion of the missile’s warhead, apparently a dummy one, at the set altitude.

Kim, the professor, said the missile’s estimated 600-kilometer (370-mile) flight indicated the launch could be a test of exploding a nuclear weapon above South Korea’s southeastern port city of Busan, where the Reagan previously docked. He said the missile tested appeared to be a new version of North Korea’s highly maneuverable KN-23 missile, which was modeled on Russia’s Iskander missile.

North Korea described the missile that flew over Japan as a new-type intermediate-range weapon that traveled 4,500 kilometers (2,800 miles). Some foreign experts earlier said the missile was likely North Korea’s existing nuclear-capable Hwasong-12 missile, which can reach the U.S. Pacific territory of Guam. But Kim, the professor, said the missile tested recently appeared to be an improved version of the Hwasong-12 with a faraway target like Alaska or Hawaii.

North Korea released a slew of photos on the launches. One of them showed Kim and his wife Ri Sol Ju, both wearing ochre field jackets, frowning while covering their ears. Some observers say the image indicated Ri’s elevated political standing because it was likely the first time for her to observe a weapons launch with her husband.

Worries about North Korea’s nuclear program deepened in recent months as the country adopted a new law authorizing the preemptive use of its bombs in certain cases and took reported steps to deploy tactical nuclear weapons along its frontline border with South Korea. This year, North Korea carried out more than 40 missile launches.

Some experts say Kim Jong Un would eventually aim to use his advanced nuclear arsenal to win a U.S. recognition of North Korea as a legitimate nuclear state, which Kim sees as essential in getting crippling U.N. sanctions on his country lifted.

Kim Jong Un said the recent launches were “an obvious warning” to Seoul and Washington, informing them of North Korea’s nuclear attack capabilities. Kim repeated that he has no intentions of resuming the stalled disarmament diplomacy with the United States now, according to KCNA.

“The U.S. and the South Korean regime’s steady, intentional and irresponsible acts of escalating the tension will only invite our greater reaction, and we are always and strictly watching the situation crisis,” Kim was quoted as saying.

Kim also expressed conviction that the nuclear combat forces of his military would maintain “their strongest nuclear response posture and further strengthen it in every way” to perform their duties of defending the North’s dignity and sovereign rights.

South Korean officials recently said North Korea maintains readiness to perform its first nuclear test in five years. Some experts say the nuclear test would be related to an effort to build warheads to be mounted on short-range missiles targeting South Korea.

“North Korea has multiple motivations for publishing a high-profile missile story now,” said Leif-Eric Easley, a professor at Ewha University in Seoul. “Kim Jong Un’s public appearance after a month-long absence provides a patriotic headline to mark the founding anniversary of the ruling Workers’ Party.”

“Pyongyang has been concerned about military exercises by the U.S., South Korea and Japan, so to strengthen its self-proclaimed deterrent, it is making explicit the nuclear threat behind its recent missile launches. The KCNA report may also be a harbinger of a forthcoming nuclear test for the kind of tactical warhead that would arm the units Kim visited in the field,” Easley said.