At least eight people were killed on Tuesday when two huge bombs went off near Mogadishu's airport, including one close to the UN's political office in the Somali capital, a security source said.
An AFP journalist at the scene heard gunfire after the explosions tore through the area, one of which was believed to be a car bomb.
Somalia's Al-Qaeda-linked Shabaab has carried out a string of similar attacks.
The city's airport is heavily fortified and adjoins the capital's main base for the African Union mission to Somalia, the 22,000-strong force backing the government in the battle against Shabaab insurgents.
The jihadists were chased out of Mogadishu in 2011 but remain a serious threat in both Somalia and neighbouring Kenya, where they carry out frequent attacks.