Submarine No. 841 will be one of the main "underwater offensive means of the naval force" of North Korea. (Photo: Reuters)

North Korean leader Kim Jong Un, who attended the launch ceremony on Wednesday, said arming the navy with nuclear weapons was an urgent task and promised to transfer more underwater and surface vessels equipped with tactical nuclear weapons to the naval forces, news agency KCNA reported.

Submarine No. 841 -- named Hero Kim Kun Ok after a North Korean historical figure -- will perform its combat mission as "one of core underwater offensive means of the naval force" of North Korea, Mr. Kim said.