Kim issued the directive, according to state-run Korean Central News Agency (KCNA), after he oversaw the first day of a two-day weapons test of North Korea's latest destroyer, the Choe Hyon.

"Saying that the time has come to make a responsible option for accelerating the nuclear armament of the navy in order to defend the state and maritime sovereignty from the existing and future threat, he set forth different tasks for realizing it," KCNA reported.

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

The warship, named after a deceased North Korean anti-Japanese fighter, is a 5,000-ton destroyer-class vessel that took more than a year to build, according to KCNA.

Given its size, experts believe the vessel can carry both ship-to-surface and ship-to-air missiles, with specialist outlet NK News reporting it is "likely to be equipped with short-range tactical nuclear missiles".

KCNA said Wednesday that the "test-fire of supersonic cruise missile, strategic cruise missile, anti-aircraft missile and 127 mm ship-based automatic gun took place on April 28."

"On April 29, the test-fire of ship-to-ship tactical guided weapon, various kinds of ship-based automatic guns and smoke and electronic jamming guns took place," KCNA added.

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, around the Korean Peninsula 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.