North Korea tested nuclear-capable rocket launchers Saturday, state media reported Sunday, a day after Seoul detected about 10 ballistic missile launches.

The drills come as U.S. and South Korean forces conduct their springtime exercises, “Freedom Shield,” involving 18,000 troops through March 19.

North Korean leader Kim Jong Un oversaw the test of a multiple rocket launcher system, KCNA said, involving 12 600mm-caliber ultra-precision launchers and two artillery companies.

Kim said the exercise gave Pyongyang's enemies, within 420 kilometers (260 miles) of striking range, a sense of "uneasiness" and "a deep understanding of the destructive power of tactical nuclear weapon." He praised the system as a "very deadly yet attractive weapon."

The rockets hit an island target in the East Sea more than 360 kilometers away. KCNA released photos showing rockets blasting off and Kim watching with his daughter Ju Ae, who is widely seen as next in line to lead North Korea.

South Korea’s Joint Chiefs of Staff confirmed multiple launches into the East Sea, also known as the Sea of Japan. Seoul’s Blue House called them a "provocation that violates United Nations Security Council resolutions" and urged Pyongyang to stop such acts.

The launches came hours after South Korean Prime Minister Kim Min-seok said U.S. President Donald Trump thinks a meeting with Pyongyang’s Kim would be "good." Kim has said the two nations could "get along" if Washington accepted North Korea’s nuclear status.

Kim’s comment on the rocket launch appeared linked to the joint drills, Hong Min, a senior analyst at the Korea Institute for National Unification, told AFP. "The launch pattern... is closely synchronised with the schedule," he said. "This suggests the weapons system is being operated as a means of nuclear deterrence and practical demonstration."

Earlier this week, Kim Yo Jong, a close confidante of her brother, warned the drills "may cause unimaginably terrible consequences," calling them a threat at "a critical time when global security structure is collapsing rapidly and wars break out in different parts of the world."

North Korea has also condemned the U.S.-Israeli attack on Iran as an "illegal act of aggression" and recently tested missiles from the Choe Hyon destroyer, claiming it is "arming the Navy with nuclear weapons."