The Yongbyon nuclear complex was closed in 2007 and North Korea had previously threatened to reopen it, particularly in 2013 after the country's third nuclear test. The director of North Korea's Atomic Energy Institute, unnamed in comments quoted by KCNA and reported by Sky News, said that its scientists had "made innovations day by day" in order to "guarantee the reliability of the nuclear deterrent...as required by the prevailing situation." (READ MORE)