This weekend, Pyongyang had unveiled its new warship, a 5,000-ton destroyer-class vessel named Choe Hyon, which some analysts said was likely to be equipped with short-range tactical nuclear missiles.

Kim oversaw the first day of a two-day weapons test of the destroyer, the official Korean Central News Agency said.

He then ordered officials to work on "accelerating the nuclear armament of the navy", it added.

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

Experts have said that given its size, the warship is believed to carry both ship-to-surface and ship-to-air missiles.

KCNA said Tuesday's test was of "ship-to-ship tactical guided weapon, various kinds of ship-based automatic guns and smoke and electronic jamming guns," involving the newly unveiled vessel.

The news agency said Pyongyang also tested its "supersonic cruise missile, strategic cruise missile, anti-aircraft missile and 127 mm ship-based automatic gun" on Monday.

Kim said the country's ship-based firepower system was "effectively combined" with the "most powerful strike means including supersonic cruise missile, strategic cruise missile and tactical ballistic missile".

Seoul's defence ministry said it was "closely tracking and monitoring the North Korean military's shipbuilding and development trends," in cooperation with the United States.

Pyongyang's announcement came days after it confirmed for the first time it had deployed troops to Russia to support Moscow in its war in Ukraine.

Moscow also said Saturday that North Korean soldiers "provided significant assistance in defeating the group of Ukrainian armed forces".

Some analysts say Pyongyang appears to have acquired certain weapons from Moscow to equip its warships, possibly in exchange for deploying troops.

"It seems that North Korea has recently imported several modern weapons from Russia," Ahn Chan-il, a defector-turned-researcher who runs the World Institute for North Korea Studies, told AFP.

The North has also "assembled them, and used them effectively to strengthen internal unity and boost military morale," he added.

- Kim at launch -

State media had reported Saturday on the launching of the Choe Hyon, showing images of Kim attending a ceremony with his daughter Ju Ae, considered by many experts as his likely successor.

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.

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

Pyongyang has claimed in previous years 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.

"North Korea's mention of its accelerated naval nuclear armament is presumed to refer to enhanced operational capabilities of tactical nuclear and strategic missiles by the fleet," said Yang Moo-jin, president of the University of North Korean Studies in Seoul.

This week's test appears to highlight North Korea's assertion that its newly unveiled warship is capable of blue-water operations, he told AFP, referring to naval missions conducted far from a country's own coastal waters, often in open ocean areas.