tripoli gunmen fatally shoot mayor libya third-largest city misrata late sunday ambush car inside city security officials say north african oil producer chaos since 2011 uprise unseat muammar gaddafi misrata libya big port relative peaceful gunmen chase car mayor mohamed eshtewi leave misrata airport follow arrival plane turkey security official say add unclear behind october bomb explode city court kill four people wound 40 others attack claim islamic state misrata almost 200 km 125 miles east tripoli gateway food import libya country tax-free zone one place still frequent foreign business people fear poor security elsewhere gunmen assassinate mayor libya 's big port city