unite nations congolese president joseph kabila tell annual gather world leaders unite nations saturday would ensure responsible kill two u.n. investigators early year would punish michael sharp american coordinator independent sanction monitor group zaida catalan swede kill central congo march 12 carry investigations report u.n. security council body sharp catalan find shallow grave two weeks late determine ensure light shed exact circumstances crime ensure horrendous act ... remain unpunished kabila say exactly open public court process work toward several weeks follow arrest majority suspect crimes tell 193-member general assembly congolese authorities arrest nine suspect kill western governments right group skeptical real mastermind identify internal u.n. inquiry find sharp catalan murder group congolese likely militia members central democratic republic congo absence evidence preclude possibility others involve u.n. security council meet last month unite state britain france sweden japan urge u.n. secretary-general antonio guterres establish follow-up investigation determine responsibility guterres say plan discuss establishment follow-on mechanism board inquiry congo officials council members effective would integration independent experts congolese system know whether possible guterres tell reporters last week otherwise take initiative colleagues department political affairs make necessary consultations put place system effective possible truth know say central congo kasai provinces sharp catalan kill insurrection kamuina nsapu militia demand withdrawal congolese force area drive 1.4 million people home kill 3,000 since august last year kabila say country fall victim terrorist attack mystical religious tribal militia use civilian population include children human shield kasai pose congo big security challenge scene grow humanitarian disaster country militia violence since kabila refuse step december raise fear slip back civil war kabila also tell u.n. general assembly congo far register 42 million 45 million voters national election commision would soon publish electoral calendar timelines despite progress challenge organize elections country remain great logistical level well financial security legislative one say affirm certainly move towards credible transparent peaceful elections say vote would take place year require deal congo opposition allow stay power beyond expiry mandate last december congo president say whoever kill u.n. experts punish