At least 14 people were killed and 15 others injured in an attack carried out by Islamic militants on the UN Development Program office in Somali capital Mogadishu on Wednesday.
The casualties included seven militants, foreigners and security guards, reports quoting Somali interior minister Abdikarim Hussein Guled said.
Al Qaeda-linked militant group Al-Shabaab claimed responsibility for the attack.
According to the UN Assistance Mission in Somalia (UNSOM), a pickup truck rigged with explosives was detonated outside the gate of the UN Common Compound around 11:30 in the morning, and it was followed by gunmen entering the building. There was an hour-long gun-battle and further explosions, as staff took refuge in secure areas.
The United Nations Common Compound houses UN personnel working on humanitarian and development issues for the Somali people.
Top United Nations officials have voiced their outrage at the deadly attack on the world body's compound, while reiterating that it will not deter the Organization from helping the country as it proceeds on the path to stability and development.
"This was an act of blatant terrorism and a desperate attempt to knock Somalia off its path of recovery and peace building," the NU Secretary-General's Special Representative and head of UNSOM, Nicholas Kay, said in a statement.
Secretary-General Ban Ki-moon, who is on an official visit to China and spoke by telephone with Somalia's President, Hassan Sheikh Mohamud, said he was deeply concerned and outraged by the "despicable" attack against the UN.
He urged the President to ensure that UN staff are protected, and said the Organization would not be deterred from delivering its mandate.
Deputy Secretary-General Jan Eliasson, in remarks at a Security Council debate in New York, noted that full details of the attack are still emerging, but that several people are known to have died.
Kay noted that the vast majority of UN staff are unhurt.
Following two decades of strife and humanitarian crises, Somalia entered a new phase in its history last year with the establishment of a representative Government and the approval of a draft constitution.
UNSOM, a political mission supported by the Department of Field Support (DFS), began operations earlier this month. It is tasked by the UN Security Council to offer expertise in areas ranging from the political process to disarmament to help the country consolidate and build on hard-won gains towards peace, reconciliation and stability.
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