North Korean state media KCNA on Tuesday showed Kim inspecting the submarine, and said its operational deployment in the waters of Sea of Japan (called the East Sea on the Korean Peninsula) is "near".
Kim learned about its operational and tactical data and combat weapons system after the submarine was built under his "special attention", KCNA said.
"He expressed great satisfaction over the fact that the submarine was designed and built to be capable of fully implementing the military strategic intention of the Party under various circumstances," KCNA said referring to Kim.
The images show the submarine in a covered dry dock facility, but neither the date of Kim's visit nor the location of the vessel were disclosed by the state media.
Experts indicated that the location could be the Sinpo South Shipyard and the submarine could be an updated version of the Sinpo-C class, NK News reported.
In June, specialist website 38 North reported that there was "continuing submarine construction of possibly another SINPO-class ballistic missile submarine" at the base.
Tuesday's report highlighted the potential continued progress of a submarine-launched ballistic missile (SLBM) programme, while a recent agreement with US President Donald Trump on the inter-Korean border to resume denuclearization dialogue does not appear to have begun, Efe news reported.
The report of the new submarine coincides with US National Security Adviser John Bolton's Seoul visit. He has been harshly criticized by Pyongyang for his insistence on North Korea completely denuclearizing before the US withdraws any sanctions.
Pyongyang, has reiterated that it wants a gradual denuclearization process accompanied by the progressive lifting of sanctions.
The two sides clashed at the failed Hanoi summit in February, and after the recent impromptu summit on July 31 between Kim and Trump, they announced they would resume working-level dialogue to come to a denuclearization agreement by mid-July. However no such meetings have so far taken place.
( With inputs from IANS )