MOGADISHU (Reuters) - An unmanned US spy drone has crashed in Somalia's southern port city of Kismayu, a bastion of the Al-Qaeda-allied al Shabaab group, a rebel official and residents said. The incident over the weekend came as residents cited an increase in the frequency of drones flying over Kismayu in the past few weeks. The US embassy in Nairobi declined to comment immediately. "This plane was a spy for the American govt and by the will of Allah, it crashed near the airport," al Shabaab official Sheikh Ibrahim Guled told Reuters on Monday. "We did not target it but it fell down," he said, although the group's radio station in Kismayu said the drone was shot down by its militants as it patrolled above the airport. A Kismayu resident also confirmed he saw the crashed drone. "I saw the plane at the police station ... We did not see any damage on it," he said, suggesting a technical fault may have caused the crash. The US has authorised covert operations in the Horn of Africa nation in the past. US special forces killed one of east Africa's top Al-Qaeda militants, Kenyan-born Saleh Ali Nabhan, in Somalia in Sept 09.