Mortar bombs killed at least 30 people in Somalia's capital Mogadishu Thursday after rebels launched shells at the president's plane and African Union (AU) peacekeepers responded with heavy artillery fire. President Sheikh Sharif Ahmed, who was leaving for a summit in Uganda, was not hurt. But residents and medical workers said at least 30 people died and scores more were wounded in one of the heaviest exchanges to rock the city for weeks. Farah Olow, a shopkeeper in the sprawling Bakara market, told Reuters by telephone that six people were killed by one shell that demolished a home there. “They were taking cover in a concrete building, but such big shells can penetrate the strongest house,” he said. “We can't go out to count how many more are dead. Bombs are raining on us.” Ali Yasin Gedi, vice chairman of Mogadishu's Elman Peace and Human Rights Organization, said the insurgents had opened fire as the president's plane was leaving the coastal airstrip. “Insurgents fired mortar bombs at the plane carrying President Ahmed, and then AMISOM responded with shells. That is how the problem started,” Gedi said.