dakar christian militiamen kill mauritanian u.n. peacekeeper attack camp displace people central african republic diamond-mining town monday unite nations mission say fighters arm ak-47s makeshift weapons also wound one zambian two mauritanian peacekeepers 90-minute gunfight police checkpoint town bria u.n. add country rive sectarian conflict since 2013 muslim seleka rebel oust president francois bozize trigger backlash christian anti-balaka fighters many 100 people die bria june day clash rival factions area covet militia surround diamond mine also host tens thousands people displace conflict even 13,000 troop u.n. mission struggle restore order country size france lose 14 peacekeepers attack year alone militants kill u.n. peacekeeper central african republic