Kim Jong Un has called for boosting North Korea's navy, state media reported Tuesday, saying the country's waters brimmed with "the danger of a nuclear war".

The North Korean leader slammed growing trilateral cooperation between the "gang bosses" of the United States, South Korea and Japan, who are holding joint naval drills.

He accused Washington of being "more frantic than ever before" by conducting joint naval exercises and deploying nuclear strategic assets in the waters around the Korean peninsula on a permanent basis, the report said.

"Owing to the reckless confrontational moves of the US and other hostile forces, the waters off the Korean Peninsula have been reduced into the world's biggest war hardware concentration spot, the most unstable waters with the danger of a nuclear war," Kim said, according to KCNA.

"To achieve the successes in rapidly developing the naval force has become a very urgent issue in view of the enemies' recent aggressive attempts."

Photos carried by the official Rodong Sinmun newspaper showed Kim, accompanied by his young daughter, inspecting the navy command and taking photos with scores of naval officers.

The United States, South Korea and Japan held a joint naval missile defence exercise on Tuesday to counter Pyongyang's growing nuclear and missile threats.

The United States and South Korea are also holding their annual Ulchi Freedom Shield exercises, which always infuriate Pyongyang.

North Korea has conducted a record number of weapons tests this year, and last week carried out its second attempt to put a spy satellite into orbit, although it ended in failure.

Kim has declared North Korea an "irreversible" nuclear power and has called for ramped-up arms production, including tactical nuclear weapons.