North Korea's Kim oversees simulated nuclear counterattack against US, South Korea

North Korean leader Kim Jong Un has overseen drills simulating a nuclear counterattack against the US and South Korea in a warning to the allies who are scaling up their joint military exercises, state media KCNA said on Monday.

The North's drills involved a short-range missile launch but - unusually - the missile flew from a buried silo, which analysts say would help improve speed and stability in future tests of intercontinental ballistic missiles (ICBM).

KCNA said the exercises on Saturday and Sunday were designed to boost the country's "war deterrence and nuclear counterattack capability," accusing Washington and Seoul of making an "explicit attempt to unleash a war" against it.

"The drill also aimed to demonstrate our tougher will to make an actual war response and send a stronger warning to the enemy who expand their war drills for aggression," KCNA said.

In the exercises, a ballistic missile equipped with a mock nuclear warhead flew 800 km (497 miles) before hitting a target under the scenario of a tactical nuclear attack, KCNA said.

KCNA photos showed Kim attended the test, again with his young daughter, as flames roared from the soaring missile before it hit the target.

Analysts said the photos suggested the launch involved a KN-23 short-range ballistic missile (SRBM), but unlike past tests, the engine exhaust appeared to be vented either side at the moment of liftoff, which could mean that a silo was used.

"Until now, North Korea has preferred mobile launchers for everything from SRBMs to even huge ICBMs, but given its poor road and system conditions, it was difficult to guarantee the stability of the missile during actual operations," said Yang Uk, a fellow at the Asan Institute for Policy Studies in Seoul. "The latest launch might possibly serve as a test for future launches of larger missiles like the Hwasong-17 ICBM in a silo."

South Korea's defence ministry spokesman said the North is making significant technological advances in its nuclear programme but did not elaborate.

'Nuclear war deterrence'

Kim said the exercises improved the military's war capability and urged the military to stand ready for any "immediate and overwhelming nuclear counterattack anytime."

"The present situation, in which the enemies are getting ever more pronounced in their moves for aggression against the DPRK, urgently requires the DPRK to bolster up its nuclear war deterrence exponentially," KCNA quoted him as saying.

Kim was using the acronym of his country's official name, the Democratic People's Republic of Korea.

"The nuclear force of the DPRK will strongly deter, control and manage the enemy's reckless moves and provocations with its high war readiness, and carry out its important mission without hesitation in case of any unwanted situation," he added.

South Korea and Japan reported a launch of a North Korean short-range ballistic missile off the east coast on Sunday, the latest in a series of missile tests in recent weeks.

North Korea has reacted furiously to South Korea-US combined military drills, calling them a rehearsal for invasion against it.

The allies have been carrying out exercises this month, including air and sea drills on Sunday involving US B-1B bombers.

The US and South Korea navies and marine corps are set to kick off their first large-scale Ssangyong amphibious landing exercises in five years on Monday for a two-week run until April 3.

Last month, the two countries staged tabletop exercises simulating North Korea's nuclear attack amid South Korean President Yoon Suk Yeol's push for more confidence in US extended deterrence - its military capability, especially nuclear forces, to deter attacks on its allies.

In another dispatch, KCNA said more than 1.4 million North Koreans have volunteered to join or re-enlist in the military to fight against Seoul and Washington, up from about 800,000 reported by a state newspaper just two days before.