North Korean held a launching ceremony for a new submarine it said was capable of tactical nuclear attacks, a move that could increase its ability to carry out atomic strikes in the region.

The country’s state media released photos Friday of the ceremony for the vessel that was attended by leader Kim Jong Un, who said he wanted to push forward with increasing his navy’s ability to use nuclear weapons. South Korea’s military expressed doubts about the capabilities of the vessel.

The initial images showed the submarine likely has 10 tubes for missiles and is a modernized Soviet-designed Romeo Class boat, specialist publication Naval News said in an analysis. This would be an improvement over North Korea’s only other sub for missile strikes that the Nuclear Threat Initiative said appears able to launch just a single ballistic missile.

“The submarine-launching ceremony heralded the beginning of a new chapter for bolstering up the naval force of the DPRK,” the official Korean Central News Agency reported, referring to the country by its formal name. Kim said the submarine would be named “Hero Kim Kun Ok” and “will perform its combat mission as one of core underwater offensive means of the naval force of the DPRK,” the report said.

South Korea’s military said it does not believe the submarine is ready for deployment and North Korea may be trying to hide some of its shortcomings.

“Based on our analysis of the North Korean submarine’s appearance to date, it appears to have increased the size and shape of some parts, such as the bridge, in order to carry missiles,” the Joint Chiefs of Staff said in a statement. “But we do not believe that it can be operated normally, and there are signs of deception or exaggeration,” it said.

The new submarine appears externally to have 10 launch tubes, with four being slightly larger, said Ankit Panda, a senior fellow in the nuclear policy program at the Carnegie Endowment for International Peace. This suggests that two separate missile types will be deployed.

“This doesn’t fundamentally change the nature of the challenge posed by North Korea’s nuclear forces, but it broadly increases the complexity of the threat in wartime,” Panda said.

The new submarine appears to be conventionally powered but Kim has made it a goal to develop a nuclear-powered sub. North Korea has one of the world’s largest sub fleets but most of its vessels are small, old and “designed to disrupt sea lanes, lay mines, attack surface vessels, and assist special operations units’ infiltration,” according to a white paper from South Korea’s Defense Ministry.

Its current fleet of submarines also makes enough noise underwater that the vessels are unable to stray far from the coast without being tracked.

North Korea for years has been working on a deploying a second submarine that can fire missiles and Kim was seen in an image released by state media about four years ago inspecting a vessel under construction. Pyongyang has also been working on new types of compact ballistic missiles for submarines and those would likely be used in the new boat.

The photographs released several years ago of the submarine under construction appeared to show a modified version of the diesel-electric Romeo-class vessels that comprise about one-third of the Korean People’s Navy submarine fleet, said Joseph Dempsey, a research associate for defense and military analysis at the International Institute for Strategic Studies.

He said in a post on the X social media site once known as Twitter the vessel North Korea displayed in photos Friday appears to be the same, “albeit more extensively modified-submarine North Korea showed us way back in July 2019.”

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Even one submarine lurking off the Korean Peninsula, beyond the gaze of spy satellites, would present US military planners with a dangerous new threat to consider in the event of any conflict.

The ceremony took place as Kim prepares to meet Russian President Vladimir Putin in Vladivostok next week, as the US warns North Korea has been providing arms to Russia for its war in Ukraine.

Kim may be seeking technology from Russia that would help in building a nuclear-powered submarine, the New York Times reported. Russia is looking for munitions including artillery shells and anti-tank missiles from Kim.

North Korea likely timed the ceremony for the new submarine to coincide with festivities Saturday to mark the 75th anniversary of the state’s founding. China plans to send its second high-profile delegation to North Korea in less than two months for the event.

Beijing is North Korea’s biggest backer and the delegation offers China a chance to offer guidance to Kim before he meets Putin.

(Updates with South Korean military’s doubts about the submarine.)