nairobi unite state citizen work south sudan freelance journalist among 19 people kill saturday fight government troop rebel yei river state rebel military say christopher allen work various news outlets kill heavy fight town kaya south sudan convulse conflict since late 2013 pit president salva kiir troop rebel leader riek machar grind 16 body find around defensive position spla include white man santo domic chol military spokesman tell reuters three government soldier also kill say rebel identify allen embed past week sad family come tell story say one rebel know allen ask name say allen middle fight wear jacket mark press chol say rebel attack army base kaya repulse hour-long fight u.s. government respond immediately reuters seek comment country spiral civil war fight along ethnic line kiir sack machar late 2013. peace accord sign august 2015 machar return capital april last year share power kiir deal fell apart less three months late machar supporters flee capital conflict force million people flee home uganda currently host million south sudanese refugees 330,000 flee neighbor ethiopia u.s. journalist among 19 kill south sudan fight rebel