VIENNA (Reuters) - North Korea's third nuclear test and threats of military action are "completely unacceptable", U.N. Secretary-General Ban Ki-moon said in remarks published on Saturday, urging Pyongyang to feed its people and seek peace with South Korea. North Korea threatened the United States on Thursday with a pre-emptive nuclear strike and has scrapped the armistice with Washington that ended hostilities in the 1950-53 Korean War. That followed its third nuclear test on February 12, in defiance of U.N. resolutions, drawing further U.N. ...