The AU says that three peacekeepers and five Islamist gunmen were killed in the ensuing battle, which saw the gunmen infiltrate the base in Mogadishu.
An alleged senior member of al-Qaeda has been captured in Libya after US forces launched raids in the country and Somalia over the weekend.
Store owners and many Kenyans are angry that goods appeared to have been looted during a shooting at Westgate mall in Nairobi where 67 people died.
Somalia's al-Shabab militants continue their siege of Westgate mall in Kenya, which has left at least 68 people dead. WARNING: graphic images.
Kenya’s government suspects about 10 to 15 gunmen are behind the attack at an upmarket mall in Nairobi, which has now claimed 59 lives.
Somalia's al-Qaeda linked al-Shabab insurgents have shot and blasted their way into the UN compound in Mogadishu, leaving eight people dead.
A suicide bomber hit a convoy of cars carrying Qatari officials through the centre of Somalia's capital Mogadishu on Sunday.
Somalia's al-Shabaab fighters briefly took control of a small town on the border with Kenya in a battle that left at least 12 people dead.