SANAA - A car bomb outside a military base in the Yemeni southern port city of Aden killed at least 6 and injured 15 on Sunday, a medical source said.Witnesses also reported they saw a tank on fire.The blast comes after an explosion in a booby-trapped car killed a Briton in Aden on Wednesday.The country has been hit by months of political unrest against the 33-year rule of President Ali Abdullah Saleh.