niamey gunmen pick-up truck motorcycle come mali kill 13 gendarmes wound five attack base western niger security source say saturday village dozen kilometers miles militants kill four u.s. soldier ambush oct. throw spotlight u.s. counter-terrorism mission niger country straddle expanse sahara niger military officials confirm attack assailants cross border mali drive village ayorou 40 km 25 miles inside spring attack security source say heavily arm rocket launchers machine gun come four vehicles seven fighters say security source scene reinforcements late arrive stop try cross back border another security source scene say trigger gun battle escape mali pursue add land air force pursue assailants view neutralise statement niger military say confirm death toll initial attack one assailants kill exchange fire others manage make four nigerien army vehicles first security source say since take swathe northern mali 2012 scatter french-led counter-offensive follow year islamist militants establish lawless space across desert use areas springboard wave attack threaten destabilize west africa fighters inflict damage military outposts kill security officials civilians kidnap westerners sometimes mount high-profile attack hotels resort across region include burkina faso ivory coast several islamist group well-armed ethnic militia operate area along mali-niger border least 46 attack since early last year however officials suspect many include ambush joint u.s.-niger patrol work islamic state great sahara lead arabic-speaking north african militant adnan walid al-sahrawi pledge allegiance islamic state militants iraq syria although extent tie know group yet claim responsibility saturday attack one kill u.s. soldier respond ever grow militant threat mali saturday announce year extension state emergency hope need continue extend state emergency defence minister tiena coulibaly tell reporters hope oct. 31 2018 order restore increasingly fluid cross-border nature militant threat force sahel countries mali niger chad mauritania burkina faso launch joint force know g5 sahel july try good coordinate police desert yet receive commitment fraction donor fund need u.n. security council delegation mali saturday discuss force tragedy one element ... underline urgency strong determine response creation joint g5 sahel force french permanent representative u.n. francois delattre tell journalists meet gunmen kill 13 niger gendarmes attack near mali border