The US military launched an air strike in Somalia on Monday targeting a senior leader of the al-Qaida-aligned al Shabaab militant group, the Pentagon said."The strike took place in the vicinity of Saakow, Somalia," Defense Department spokesman Mark Wright said in a statement. "At this time, we do not assess there to be any civilian or bystander casualties. We are assessing the results of the operation and will provide additional information, when appropriate, as details become available."Al Shabaab is seeking to topple the Western-backed Mogadishu government and impose its own strict version of Islamic law in the country.