Four African Union peacekeepers were killed when a mortar hit Somalia’s presidential palace, officials say.
It is not clear if any Somalis were hit by the shells, fired as Islamist insurgents continue to battle government forces.
Those killed were from Uganda, one of just two countries to have sent troops to Somalia to help the government.
Last month, at least 76 people were killed in Uganda in bombings which a Somali group said it had carried out.
The battle for control of Mogadishu has intensified in the past week.
Last Monday, a suicide attack on a hotel killed at 32 people, including six MPs.
The Islamist group al-Shabab said it had carried out the attack, as it had the bombings in the Ugandan capital, Kampala, as people watched the World Cup final.
Al-Shabab, which has links to al-Qaeda, controls much of southern and central Somalia, while the government is confined to a few pockets of the capital.
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