abuja nigeria president muhammadu buhari appeal calm end communal violence saturday police say arm herdsmen kill 19 people central state plateau local police say fulani herdsmen attack ancha village bassa local government area plateau state early hours friday say think reprisal attack boy herd community kill police provide detail attack five people injure late friday fight semi-nomadic cattle herders settle communities land use claim hundreds live year nigeria central northern state urge communities state part country embrace peace bring stop painful unnecessary kill say buhari email statement say communities security agencies plateau take step pull state back brink anarchy senseless kill add would painful loss allow unsavory act return violence another security challenge buhari addition eight-year boko haram jihadist insurgency northeast attempt maintain fragile ceasefire southern niger delta energy hub militant attack oil facilities last year cut crude production third nigeria 's buhari urge calm herdsmen kill 19 central plateau state