At a ceremony to launch a new 5,000-ton destroyer in the eastern port city of Chongjin on Wednesday "a serious accident occurred," the official Korean Central News Agency said.

Blaming "inexperienced command and operational carelessness" during the launch, which was being observed by Kim, KCNA said there was a mishap which left "some sections of the warship's bottom crushed".

It said the accident managed to "destroy the balance of the warship."

Kim watched the entire incident and declared it a "criminal act caused by absolute carelessness," warning it "could not be tolerated."

He said the "irresponsible errors" of officials responsible would be "dealt with at the plenary meeting of the Party Central Committee to be convened next month".

Pyongyang unveiled another 5,000-ton destroyer-class vessel named Choe Hyon last month.

At the time, state media ran images of Kim attending a ceremony with his daughter Ju Ae, considered by many experts to be his likely successor.

North Korea claimed the vessel was equipped with the "most powerful weapons", and that it would "enter into operation early next year".

Some analysts said the ship could be equipped with short-range tactical nuclear missiles -- although North Korea has not proven it has the ability to miniaturise its nukes.

- Russian connection? -

The South Korean military has said the Choe Hyon could have been developed with Russian help -- possibly in exchange for Pyongyang deploying thousands of troops to help Moscow fight Kyiv.

Ahn Chan-il, a defector-turned-researcher who runs the World Institute for North Korea Studies, said the newly built warship may also have been constructed with Russian assistance.

Chongjin, the North Korean city where the launch ceremony was held, is conveniently close to Russia's Vladivostok port, he noted.

"It's also likely that the projected timeline for the vessel -- including when assembly would be completed and the ship launched -- was shared with the Russian side," he told AFP.

"It appears the dock was hastily constructed, and multiple issues may have arisen during the shipbuilding process.

"With today's announcement, Pyongyang seems to be signalling not only to its own people, but also to the Russian side."

- Strengthening the navy -

North Korea confirmed in April for the first time it had deployed troops to Russia to support Moscow in the Ukraine war.

Moscow and Pyongyang recently announced that they had started building the first road bridge linking the two neighbours.

North Korea also launched a flurry of ballistic missiles last year in violation of UN sanctions.

Experts have long warned that the nuclear-armed North may be testing weapons for export to Russia for use against Ukraine.

In March, Kim inspected a project to build a nuclear-powered submarine, asserting that "radically" boosting the navy was a key part of Pyongyang's defensive strategy.

Kim called at the time for the modernisation of the country's surface and underwater naval forces, including the development of warships.

Pyongyang has previously claimed to be developing underwater nuclear attack drones, which could unleash a "radioactive tsunami", but analysts have questioned whether it actually has such a weapon.

Washington -- Seoul's key security ally -- has in recent years ramped up joint military exercises and increased the presence of strategic US assets, such as an aircraft carrier and a nuclear-powered submarine, in the region to deter the North.

Pyongyang has repeatedly declared itself an "irreversible" nuclear weapons state and routinely denounces joint US-South Korea drills as rehearsals for invasion.