Undated photos of North Korean leader Kim Jong-un visiting a submarine were released on July 16.
Reuters reported that the leader visited the submarine while making an inspection of the Korean People's Army Naval Unit 167. It also said Kim gave field advice while visiting the facility.
No details were given about the submarine.
North Korea had alleged that South Korea was producing nuclear submarines. Last year, South Korea and the United States launched a joint naval exercise involving a US nuclear submarine before a nuclear test by the North.