A North Korean navy truck carries the 'Pukkuksong' submarine-launched ballistic missile (SLBM) during a military parade marking the 105th birth anniversary of country's founding father, Kim Il Sung in Pyongyang, April 15, 2017. North Korea has escalated tests of its SLBM programme in the last year. Whilst the isolated country is not yet believed to have an operational submarine capable of carrying more than one missile at the time, its enemies are worried that a fully-functional SLBM would make tracking and intercepting a North Korean missile launch and the submarine from which it was fired very difficult. REUTERS/Damir Sagolj TPX IMAGES OF THE DAY SEARCH "PARADE WID" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES.