KISMAYU, Somalia, Feb 11 (Reuters) - An explosion killed at least four people in Somalia on Sunday and wounded 24 others including senior military officers and regional leaders at a ceremony in a southern port, witnesses said. "I saw two dead clan elders, one dead civilian and one government soldier," said Abdulahi Mohamed, who was in the crowd at Kismayu's Independence Gardens. "Twenty-four people were wounded, including some senior military officials."