mandra greece flash flood kill least 15 people make score homeless destroy infrastructure greece wednesday rag torrent inundate two coastal towns west athens follow night heavy rain devastation locals say unprecedented scale overnight deluge trigger flash flood industrial towns nea peramos mandra foothills mountain west athens prime minister alexis tsipras declare period national mourn difficult moments greece live great disaster say state address immediately without delay support measure adopt households businesses affect say without go detail residents say wake wednesday morning rainwater mud come home scale destruction become clear day large areas cover water mud areas floodwaters rise first story small build incredible amount water cause rag torrents say yiannis kapakis head greece civil protection service torrential rain type uncommon greece poor infrastructure leave citizens vulnerable flood rain steadily week country meet office issue new severe weather warn thursday residents force onto rooftops balconies cars thrust onto porches home ram like dodgem vehicles tree trunks tip onto side biblical disaster mandra mayor yianna krikouki tell state broadcaster ert everything go attica prefecture administrative district towns say would seek assistance eu solidarity fund set respond natural disasters state emergency declare region wall collapse cars carry away break everything nothing leave resident marina kolia say water everywhere house mandra nea peramos combine population 20,000. many greek house settlements build without take account town plan regulations athens prosecutor order urgent preliminary investigation deaths destruction cause also investigate possible urban plan offences tuesday greece declare state emergency eastern island symi coast turkey storm sweep cars sea damage home cut electricity water supply least 15 dead flash flood greek coast