Threat level was high before UN attack in Somalia that killed 8 UN staff, 5 civilians

A U.N. official says that in the weeks preceding Wednesday's attack against a U.N. compound in Somalia's capital the threat level had been elevated.

The official said Thursday that staff in Mogadishu had been advised of threats to the airport area. Militants on Wednesday detonated a truck bomb across the street from the airport at the main U.N. compound. Gunmen then poured inside.

In all 20 people died, including eight U.N. staff, five civilians and seven al-Shabab attackers.

A second U.N. official said the Mogadishu operations have been under a consistent threat for years but that he wasn't aware of a specific elevated threat ahead of Wednesday's attack.

Both U.N. officials insisted on anonymity because they are not authorized to speak publicly.