geneva fight air strike intensify yemeni capital sanaa roads block tank deploy many streets trap civilians halt delivery vital aid include fuel supply clean water unite nations say monday fierce clash around diplomatic area near u.n. compound aid flight sanaa airport suspend world body say statement follow appeal humanitarian pause tuesday escalate situation threaten push barely function basic service ... standstill service already seriously compromise late shock impact blockade say add fight also spread governorates hajjah fight air strike yemen 's sanaa trap civilians halt aid u.n