North Korean leader Kim Jong Un has instructed officials to modernize the navy's fleet and equipment. He noted that strengthening the navy is critical for "war preparations."

The ruling Workers' Party newspaper, Rodong Sinmun, reported on Friday that Kim visited a shipyard in the western city of Nampho.

The newspaper carried photos of Kim looking at docked warships. The leader was accompanied by party officials in charge of weapons development and the navy's commander.

The media outlet quoted Kim as saying that bolstering the country's naval force is "the most important issue." He reportedly noted that it needs to be done so that maritime sovereignty can be protected and war preparations can be stepped up.

Kim has strongly condemned the US for deploying nuclear-powered submarines to the Korean Peninsula.

Last September, North Korea announced that Kim had attended a launching ceremony for a newly built "tactical nuclear attack submarine." On Sunday, state media outlets reported that Kim observed the construction of another nuclear submarine.

This year is the fourth year of Kim's 5-year defense plan. During his latest visit to the shipyard, Kim instructed workers to complete projects within the time frame. South Korean media outlets report that the Nampho Dockyard could be engaged in work related to the construction of a nuclear submarine.

South Korea's intelligence agency has claimed that North Korean hacker groups stole ship designs and other data from South Korean shipbuilders in August and September of last year.