aden suicide car bomber blow security checkpoint southern yemeni port city aden sunday kill 15 people wound least 20 residents security official say islamic state militants claim responsibility assault without provide evidence attack occur outside main security headquarter aden khor maksar district accord aden residents security official blast hear across city plume smoke could see miles away clash erupt area immediately afterward witness report unclear behind attack clash follow islamic state claim responsibility attack statement post internet though without immediate evidence back assertion say least 50 people kill blast clash al qaeda arabian peninsula aqap local branch global islamist militant network active jihadist group southern yemen recent years aden interim headquarter yemen internationally recognize government move houthi rebel take control capital sanaa 2015 yemen civil war 10,000 people kill conflict since houthis advance aden force president abd-rabbu mansour hadi flee seek help saudi arabia aden dominate yemeni force back unite arab emirates key member saudi-led coalition intervene yemen war restore hadi saudi arabia air defense force intercept ballistic missile fire yemen capital riyadh saturday state news agencies report missile bring near king khaled airport northern outskirts city cause casualties car bomber kill least 15 yemeni port aden witness