Mr Kim was seen looking over the weapon systems of the vessel built under “his special attention” in photos released on Tuesday by the state news agency KCNA.
The organisation said the submarine would soon be deployed in the waters off North Korea’s east coast, without providing any details on the weapon systems. Analysts claimed the size of the watercraft indicated it was designed to carry missiles.
“We can clearly see that it is a massive submarine – much larger than the existing one that’s been well known since 2014,” said Ankit Panda, senior fellow at the US-based Federation of American Scientists.
“What I find significant about the political messaging here is that this is the first time since a February 2018 military parade that he has inspected a military system clearly designed to carry and deliver nuclear weapons.”
Mr Panda added: “I take that as an ominous signal that we should be taking Kim Jong-un’s end-of-year deadline for the implementation of a change in US policy with the utmost seriousness.”
North Korea has a large submarine fleet, but only one known experimental submarine capable of carrying a ballistic missile.
A South Korean defence ministry spokesman said they were monitoring developments but could not confirm if the submarine was designed to carry missiles.
Mr Kim has declared a moratorium on testing ICBM’s and nuclear weapons while engaging in denuclearisation talks with the US and South Korea.
The submarine photos come amid another delay in dialogue between Washington and Pyongyang after Mr Kim and Donald Trump agreed at a meeting at the Panmunjom Korean border on 30 June to working-level nuclear talks.
Mr Trump said such talks could come in the following two to three weeks. His national security advisor, John Bolton, arrives in South Korea on Tuesday to meet security officials.
HI Sutton, a naval analyst who studies submarines, said the latest photos indicated the hull could be based on old Romeo Class submarines, which were originally acquired from China in the 1970s before North Korea began producing them domestically.
North Korea is believed to have about 20 Romeo submarines in its fleet, the newest of which was built in the mid-1990s.
Mr Sutton said the North Koreans appeared to have raised the deck on a Romeo-type design, possibly even modifying an existing Romeo to make a submarine larger than previous designs.
“I’d bet that this is indeed a missile submarine,” he said.
US-based monitoring group 38 North said in June 2018 that North Korea appeared to be continuing submarine construction at its Sinpo Shipyard of possibly another Sinpo-class ballistic missile submarine, based on commercial satellite imagery.
Additional reporting by Reuters