North Korea's Kim Jong Un visits nuclear subs as Vladimir Putin hails 'invincible' bond

North Korean leader Kim Jong Un visited a nuclear submarine factory and received a message from Russia's Vladimir Putin hailing the countries' "invincible friendship", Pyongyang's state media said Thursday. The "heroic" efforts of North Korean soldiers in Russia's Kursk region "clearly proved the invincible friendship" between Moscow and Pyongyang, Putin said in a message to Kim, according to the Korean Central News Agency (KCNA).