MOGADISHU (Agencies) - A mortar shell exploded Sunday near Somali President Abdullahi Yusuf Ahmed's plane as it was preparing to take off from Mogadishu airport, officials and witnesses said. Three shells struck the airport and one exploded near the plane just after the President boarded it and was preparing to take off, an African Union peacekeeper at the airport said on condition of anonymity. "The president was in the plane to leave when the mortars hit the area," he said. "Fortunately, nobody was hurt." "The last mortar nearly hit the plane," eyewitness Hasan Mohamed said.Somali government officials said Yusuf was leaving Mogadishu for Djibouti, where UN-sponsored negotiations aimed at bringing the western-backed government and Islamist-led opposition to talk resumed on Saturday. According to CNN, suspected fighters fired mortar rounds at the plane carrying the President, but no one - including Abdullahi Yusuf Ahmed - was harmed, a presidential spokesman said. "Al-Shaabab has actually tried to harm to president, but thank God nobody was hurt," Huubsireb said. Al-Shaabab is a Muslim group that is trying to seize control of Somalia. It is a splinter group of the Islamic Courts Union, which ousted Somalia's transitional government in 2006. The ICU was deposed in December of that year following Ethiopia's military invasion. Bloody battles between Al-Shaabab and the Ethiopian-backed government forces in Mogadishu have forced residents to flee the capital. More than 40,000 displaced civilians have taken shelter in dozens of makeshift settlements west of Mogadishu, described by the United Nations as "precarious conditions." Sunday's mortar attack is the second assassination attempt on Yusuf. The president survived a car bombing in September 2006 outside Somalia's parliament in Baidoa that killed at least eight others. Somalia's Prime Minister Ali Mohamed Gedi has been more frequently targeted by the Islamic insurgents seeking to destabilize the government. Somalia has been mired in chaos since 1991, when warlords overthrew dictator Mohamed Siad Barre and sparked brutal clan infighting. Somalia's current transitional government is trying to maintain control of the capital, with the help of the better-equipped Ethiopian forces. But the presence of the Ethiopians has united various Muslim groups in Somalia, including Al-Shaabab, who are trying to oust the Ethiopian forces and gain control of Mogadishu.