In a separate incident, anti-government fighters clashed with Ugandan peacekeeping troops manning the city’s strategic K4 junction south of Mogadishu.
"We fought them off. No one was hurt," captain Paddy Ankunda, a spokesman for African Union peacekeeping force, said.
A year ago Ethiopian troops helped the Somali government oust the Islamic Courts Union which had briefly controlled large parts of south and central Somalia.
There has been heavy fighting on the streets of Mogadishu as parts of the group remain in the area.
The fighting, which has killed about 6,000 civilians and displaced hundreds of thousands in the past year, has been described by the UN as Africa's worst humanitarian crisis.
The African Union has deployed a contingent of 1,600 Ugandan peacekeepers which has failed to stabilise the capital.
The pan-African body plans to eventually deploy 8,000 peacekeepers in the Horn of Africa country, which has seen civil unrest since the former ruler Mohamed Siad Barre was ousted in 1991.