goma democratic republic congo militia fighters eastern democratic republic congo attack u.n. peacekeeping base friday trigger clash leave two fighters dead two peacekeepers slightly wound u.n. mission say thirty-four rebel mai-mai militia kill fight congo army past week local army spokesman jules ngongo say spike violence attribute army crackdown militia harassment local residents friday attack two rebel also wound rare frontal assault u.n. force charge protect civilians congo east dozens arm group exploit mineral resources prey local residents early morning 30 mai-mai attack mission spokeswoman florence marchal tell reuters add u.n. force drive assailants immediately clear mai-mai group attack objective mai-mai comprise number arm band originally form resist rwandan invasions 1990s since morph wide variety ethnic-based militia smuggle network protection racket congo mineral-rich eastern borderlands tinderbox ethnic tensions two decades rack violence often spill across country border president joseph kabila refusal step end constitutional mandate last december fuel unrest country east war 1996-2003 kill millions center insurgency central government kill thousands since last august last week u.n. force east congo south kivu province intervene helicopters heavy machine gun help beat back advance separate rebel group strategic city uvira u.n. mission congo know monusco world large 18,000 uniform personnel billion annual budget east congo militia attack u.n. base two rebel kill