Kim Jong Un has called for an "exponential" increase in North Korea's nuclear arsenal, including mass producing tactical nuclear weapons and developing new missiles for nuclear counterstrikes, state media said Sunday.

In a report at the end of a key party meeting in Pyongyang, Kim said the country must "overwhelmingly beef up the military muscle" in 2023 in response to what it called US and South Korean hostility, the official KCNA reported.

Claiming that Washington and Seoul were set on "isolating and stifling" the North, Kim said his country would focus on the "mass-producing of tactical nuclear weapons" and develop "another ICBM (intercontinental ballistic missile) system whose main mission is quick nuclear counterstrike".

Such goals form the "main orientation" of the 2023 nuclear and defence strategy, the report said.

Military tensions on the Korean peninsula rose sharply in 2022 as the North conducted sanctions-busting weapons tests nearly every month, including firing its most advanced ICBM ever.

It capped the record-breaking year of launches by firing three short range ballistic missiles early Saturday, and conducting another rare late-night launch at 2:50 am (1750 GMT Saturday) on Sunday, Seoul's military said.

The official KCNA reported Sunday that the launches had been "a test-fire of the super-large multiple rocket launchers".

In a separate KCNA report, Kim said the weapons put South Korea "as a whole within the range of strike and (were) capable of carrying (a) tactical nuclear warhead".

North Korea was emphasising this "in order to warn of the possibility of actual action", said Yang Moo-jin, professor at the University of North Korean Studies in Seoul.

"North Korea is signalling a tactical shift of indirectly pressuring the United States by pressuring South Korea and escalating tensions on the Korean peninsula starting this year."

The launches come just days after Seoul scrambled fighter jets as five North Korean drones made an incursion into the South's airspace Monday.

- Another Ukraine? -

Lim Eul-chul, a professor at Kyungnam University, said that the North's latest statement indicated "they are preparing for the possibility of actual war beyond the collapse of inter-Korean relations".

He warned that if the US and South Korea responded, as was likely, by further ramping up military drills, tensions between the two Koreas would reach "an unprecedented level" in 2023.

"It would indeed be a reasonable prediction that the Korean peninsula could become a second Ukraine if the situation is mismanaged," he added.

In 2022, Kim said he wanted his country to have the world's most powerful nuclear force and declared the North an "irreversible" nuclear state.

North Korea has talked about mass producing nuclear weapons before, said Go Myong-hyun, researcher at the Asan Institute for Policy Studies.

"The intention is that if North Korea mass produces nuclear weapons, even without aggressive provocations, the United States will have no choice but to someday recognise North Korea as a nuclear state," he told AFP.

"Kim Jong Un's New Year message is something like 'Let's play with nuclear weapons,'" he added.

The reports come at the end of a major party meeting in Pyongyang at which Kim and other senior officials outlined their policy goals for 2023 in key areas including diplomacy, security and the economy.

In past years, Kim had delivered a speech on January 1, but he recently dropped the tradition in favour of making announcements at the year-end plenary meeting.

North Korea also plans to launch its first military satellite "at the earliest date possible", KCNA said -- a goal South Korea is also chasing, having Friday successfully tested a solid-fuel space launch vehicle.

"North Korea ended the year with a bang but its recent missile launches were not technically impressive," said Leif-Eric Easley, a professor at Ewha University in Seoul.

But the "provocations, including drone incursions, appear excessive for deterrence and may be intended to scare South Korea into taking a softer policy".

With Kim disavowing diplomacy and threatening to mass produce nuclear weapons, it is likely South Korea will double down on boosting its own defence capacities and readiness, he said.

"If China doesn't want the regional instability of an inter-Korean arms race on its doorstep, it will have to do more to restrain Pyongyang in 2023."