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As Nigeria's new president vows to crush the Boko Haram insurgency, the United Nations human rights chief wants Boko Haram's leaders held accountable for what he described as appalling violations of human rights.
Zeid Ra'ad Al Hussein cited further evidence of atrocities committed by the terrorist group, which has reportedly killed 15 thousand people since its violent emergence in 2009.
Liling Tan reports from the UN.
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