Suspected Islamist insurgents hurled at least seven grenades at a United Nations compound in the Somalil capital Mogadishu but no one was hurt.
A UN source said the attackers struck at the UN Development Programme (UNDP) offices several times overnight after ordering residents in the area to switch off their lights late last night.
"Fortunately no one was hurt as none of the employees were present at the time," the source said. UNDP officials in Somalia's capital did not immediately comment.
The interim government and its Ethiopian military allies are facing a persistent insurgency in Mogadishu by remnants of a hardline Islamist movement they routed just over a year ago.
In a separate attack late last night, officials said three men armed with pistols shot dead a district commissioner in Wabari, a southern Mogadishu neighbourhood. Local rights workers say fighting in the capital killed 6,500 people last year.