North Korean leader Kim Jong Un oversaw a test of strategic cruise missiles, state media KCNA said on Monday, as South Korea and the United States kicked off annual military drills that Pyongyang sees as a rehearsal for war.

Kim visited a navy fleet stationed on the east coast to oversee the test aboard a warship, KCNA said, without specifying the date of his trip.

The launch was aimed at verifying the “combat function of the ship and the feature of its missile system,” while improving the sailors’ capability to carry out an “attack mission in actual war”, KCNA said, noting that the ship’s missile hit its target.

Kim touted the ship for maintaining “high mobility and mighty striking power and constant preparedness for combat to cope with sudden situations,” KCNA said.

South Korea’s defence ministry said that it had detected signs of the launch, but that the claims in KCNA were “exaggerated” and “different from the facts,” without elaborating.

The latest missile test came as South Korea and the United States began the Ulchi Freedom Shield summer exercises on Monday, designed to enhance their joint responses to North Korea’s nuclear and missile threats.

Pyongyang has denounced the allies’ military drills as a rehearsal for nuclear war.

South Korea’s military has said this year’s exercises will be held on the “largest scale ever”, mobilising tens of thousands of troops from both sides, as well as some member states of the U.N. Command.

President Yoon Suk Yeol said the drills would be conducted under several contingency scenarios, including cyber, terror and drone attacks, and a disinformation campaign from the North.

“True peace is preserved only by overwhelming force, not by one-sided begging or goodwill,” Yoon told a meeting of the National Security Council. “North Korea talks about preemptive nuclear strikes and preparations for an offensive war, but we will immediately and overwhelmingly retaliate for any provocations.”

South Korean lawmakers have said the North could test-fire an intercontinental ballistic missile or take other military action to protest the allies’ drills or last week’s summit of South Korea, the United States and Japan.

North Korea has been testing what it calls “strategic cruise missiles,” which some analysts have said could be tipped with nuclear warheads, during the past two years. While modernising and bolstering its naval power, North Korea showcased a new, nuclear-capable underwater attack drone in March.

Aboard the ship, Kim vowed to reinforce the navy with “improved combat efficiency and full modern means of surface and underwater offensive and defensive” capabilities, KCNA said.

“We would put spurs to the modernisation of naval weapons and equipment, including the building of powerful warships and the development of shipboard and underwater weapon systems,” he was quoted as saying.