Islamic group Boco Haram told the BBC it carried out Friday's attack that left 23 people dead and many more injured at the U.N. offices in Abuja. Nearly half of those killed were U.N. staff members.
U.N. Secretary-General Ban Ki-moon in statements to the Security Council said the attackers managed to get through "robust" security measures in Abuja, home to 26 U.N. agencies and programs.
"This attack is therefore cause for a serious re-assessment, not just in Nigeria, and not just in high-threat locations, but worldwide," he said in his statements.
A car bomb crashed through security barriers into the reception area, witnesses told the BBC. U.S. Army Gen. Carter Ham, the top U.S. military authority working in Africa, had told the BBC earlier this month there were growing ties between Boko Haram and al-Qaida in the Islamic Maghreb, the North African branch of al-Qaida.
Ban said the attack appears to be the first one of its kind targeting an international or foreign institution in Nigeria. Analysts said the attacks were part of underlying tensions in the country, putting Muslims against Christians.