The KCNA did not disclose when or where the inspection took place, nor any other details on the submarine, though it published a few photos.
"Explaining the Party's strategic plan for the use of submarine and underwater operation, he (Kim) elaborated on the immediate duty and strategic tasks facing the field of national defense science and submarine industry to carry out the plan," the report said.
Pointing to the country's geographic circumstances "bounded on its east and west by sea," the North Korean leader "stressed the need to steadily and reliably increase the national defense capability by directing big efforts to the development of the naval weapons and equipment such as submarine," the KCNA said.
The visit marked Kim's 11th public appearance in the military field this year and the first since his Panmunjom encounter with Trump at the end of June. Kim's previous public activity in the military field was in May.
The latest inspection appears aimed at putting pressure on Washington ahead of possible talks between the two sides.
During the Panmunjom meeting, Trump and Kim agreed to resume their working-level nuclear talks after a monthslong lull following the no-deal breakdown of their Feb. summit. The talks had been expected to start in mid-July, but Pyongyang has reportedly not responded to Washington's offer for dialogue.
North Korea's foreign ministry warned last week the joint military drills between South Korea and the US slated for next month could affect the agreed-upon talks.
On Tuesday, Choson Sinbo, a pro-North Korea newspaper based in Japan, renewed the regime's call for suspension of the planned exercise and urged Washington to come up with a new proposal to move the stalled negotiations forward.
"The US should first and foremost make objective conditions and circumstances to have denuclearization dialogue and based on that, come up with a realistic proposal that the North can accept," the newspaper said.
In Washington on Monday, Trump said the two sides will meet when the North is "ready."
The US president said "very positive" correspondence was exchanged with the North recently, but said no working-level talks have been scheduled as of yet. On the same day, US Secretary of State Mike Pompeo said he hopes the North will "take a position that's different" when they return to the negotiating table.
Experts say the submarine that Kim inspected might be capable of carrying submarine-launched ballistic missiles.
"It doesn't seem like a nuclear-powered submarine, but a Sinpo-class," Professor Kim Dong-yub of the Institute for Far Eastern Studies said. "It might be one with two or three launching tubes to be used for SLBMs."
This analysis appears to be in line with a report compiled last month by 38 North, a website providing information about North Korea, which raised the possibility of the North building a ballistic missile submarine at the Sinpo shipyard on its east coast.
The visit could also be seen as an attempt to soothe the military and the public amid possible security concerns within the country over the denuclearization negotiations.
"North Korea seems to have not elaborated on the deployment of the submarine in an apparent effort not to break its promise to the US, while soothing the military and boosting internal unity," the professor said. (Yonhap)