North Korea today said it had released American citizen Otto Frederick Warmbier on humanitarian grounds. <br/><br/>Warmbier was detained in January last year and sentenced to 15 years of hard labor for trying to steal an item with a propaganda slogan. <br/><br/>According to a US official, Warmbier's release came after the U.S. State Department's special envoy on North Korea Joseph Yun, traveled to Pyongyang and demanded his release on humanitarian grounds.