An attacker Wednesday blew himself up at the entrance to the UN headquarters in the Somali capital of Mogadishu, CNN reported.
Others wearing suicide vests entered the UN compound and a gunfight ensued, said police officer Hussein Ahmed.
The compound had now been secured and was in the hands of African Union troops, according to the official Twitter account of the African Union Mission to Somalia.
The Al Shabaab militant group linked to Al Qaeda claimed responsibility.
Xinhua said the militants attacked the office of UN Development Programme (UNDP) in Mogadishu.
"The fighting with the gunmen and suicide bombers is ongoing. We have eliminated some of the attackers but the fighting is now going on," police told Xinhua.