North Korea’s apparent use of different launch methods to fire two types of cruise missiles from a tactical nuclear-capable submarine could complicate regional defence, while raising fresh questions about the operational readiness of its growing undersea arsenal, observers have said.

The North’s official Korean Central News Agency (KCNA) said on Thursday it had “test-fired two types of submarine-launched strategic cruise missiles” off its eastern coast.

The tests “contributed to inspecting the regular mobilisation readiness of underwater combat systems and honing the navy’s ability to carry out strategic missions”, KCNA said. They also demonstrated “the high reliability, dependability and capabilities of the means of war deterrence”, it said, adding that the tests “had no negative impact whatsoever on the security of neighbouring countries”.

South Korea’s military did not publicly announce the launches, sparking speculation that it might have failed to detect them. The Joint Chiefs of Staff (JCS) said on Thursday, however, that it had tracked and monitored the launches throughout.

The JCS stressed that the military did not usually disclose North Korean cruise missile launches, limiting public announcements primarily to ballistic missile tests.

Professor Yang Moo-jin of the University of North Korean Studies said the projectiles were believed to include the Pulhwasal-3-31 (Fire Arrow Type 3-31), a strategic cruise missile with a potential range of about 2,000km that could carry small nuclear warheads. “Their low-altitude, evasive flight profiles could complicate and potentially overwhelm South Korea’s and the United States’ missile defence systems,” Yang said.

The report appeared on KCNA but was not carried by the ruling Workers’ Party’s official newspaper, Rodong Sinmun, which primarily targets a domestic audience.

In a brief report comprising just four sentences, KCNA withheld technical specifications, including the missiles’ flight duration and range, unlike previous reports that publicised test results in extensive detail.

The agency, however, released several photographs showing the submarine under way, missiles emerging from the water in bursts of flame and the projectiles in cruise flight.

Experts analysing the images identified the launch platform as the Hero Kim Kun Ok, a new 3,000-tonne-class submarine. The launches marked the vessel’s first publicly reported operation since it was unveiled in September 2023, as well as the third known test of submarine-launched cruise missiles (SLCMs) since March 2023, analysts said.

Shin Jong-woo, secretary general of the Korea Defence and Security Forum, said the missiles appeared to have been launched using both vertical launch systems and torpedo tubes. “Wednesday’s launches indicate that these missiles are being prepared for operational deployment,” Shin said.

“Further test launches of submarine-launched ballistic missiles [SLBMs] are also expected.”Hong Min, a senior research fellow at the Korea Institute for National Unification, said the simultaneous launch of two missile types with different diameters, lengths and launch methods from a submarine of the Hero Kim Kun Ok class was “unprecedented”.

North Korea appeared to be combining two launch methods – vertical launch systems and torpedo tubes – Hong said, pointing to two distinct launch profiles in the released photographs. One showed a near-vertical ascent, while the other appeared to involve a launch at an angle of about 60 degrees to 70 degrees, accompanied by falling debris.

The combination of different missile types and launch methods would make it harder for adversaries to predict which missile might be fired from which launch tube, he said.

“By extending from land to the maritime domain its demonstrated ability to deploy multiple types of warheads, North Korea is seeking to increase uncertainty for potential adversaries and strengthen its deterrence,” Hong said.

The latest tests followed the first known SLCM test in March 2023, when North Korea launched cruise missiles from the ageing 8.24 Yongung (Hero) submarine.

The North described the latest launches not as development tests but as a “routine inspection of the mobilisation readiness” of its deployed forces, suggesting that it wanted to portray the weapons as approaching operational service.

Under a strategy combining lower-cost military assets with higher-end weapons, nuclear-powered submarines under construction would serve as more sophisticated platforms, while ageing but modified Romeo-class submarines could provide a larger number of relatively inexpensive assets, Hong said. The Hero Kim Kun Ok appeared designed to be not merely an interim substitute until North Korea completed a nuclear-powered submarine programme, but also a tactical nuclear platform for coastal and near-seas operations that could remain in service even after nuclear-powered submarines became available, he said.

Hong, however, cautioned against overstating the submarine’s capabilities.

“Its operational capabilities remain unproven in several key areas, including submerged launches, extended-duration patrols and the deployment of SLBMs. Its current level of combat readiness is therefore best assessed as limited operational capability,” he said.

Thursday’s tests were the latest in a series of North Korean missile launches this month, amid an intensifying arms race with South Korea, which successfully conducted the first test launch of its domestically developed hypersonic glide vehicle a week earlier.

Yang said the latest launches were part of Pyongyang’s efforts to showcase the diversity of its missile arsenal, including short-range ballistic missiles, hypersonic weapons and submarine-launched strategic cruise missiles.

“North Korea is signalling its ability to complicate or neutralise the South Korea-US missile defence network,” he said.

The tests come ahead of a planned Asia trip by US President Donald Trump, fuelling speculation about a possible resumption of diplomacy between Washington and Pyongyang.

Trump said on Monday that he might meet North Korean leader Kim Jong-un during his coming trip to attend the Asia-Pacific Economic Cooperation summit in China, scheduled for November 18-19 in Shenzhen. Asked whether he planned to meet Kim during the trip, Trump replied, “I may,” adding: “That’ll be exciting, won’t it? But I get along with him.”The two leaders met three times during Trump’s first term: in Singapore in June 2018, in Hanoi in February 2019 and at the inter-Korean border village of Panmunjom in June 2019.

On Saturday, Trump told a campaign rally in Ohio that he “gets along great” with Kim, stressing the importance of maintaining good relations with leaders of nuclear-armed countries. The latest launches could be intended in part to strengthen Pyongyang’s leverage ahead of a potential meeting, Yang said.

“The series of missile launches in October appears to be aimed at pressing Washington to recognise North Korea as a nuclear-armed state” ahead of a possible Trump-Kim meeting.