KABUL — Ten Afghan police officers were killed Sunday when a suicide bomber detonated a car bomb outside the main police compound in the southern town of Lashkar Gah, in the first major attack of its kind in an area where Afghans recently assumed full security responsibility from the NATO-led troops. The officers were on a routine patrol at the entrance of the compound when the attack happened, said Daoud Ahmadi, a spokesman for the governor of Helmand province.