The U.N. Security Council condemned early Thursday the attack in Nairobi "in the strongest possible terms" and calls for the perpetrators, organizers, financiers and sponsors to be brought to justice.

A statement Wednesday by the U.N.'s most powerful body reiterates that "any acts of terrorism are criminal and unjustifiable, regardless of their motivation."

The council also "paid tribute to Kenya's role in the fight against terrorism," particularly in the African Union peacekeeping force fighting the al-Shabab terrorist group in neighboring Somalia.

The al-Qaida-linked militants claimed responsibility for the attack on a luxury hotel and shopping complex. Kenyan authorities said 21 civilians were killed along with five attackers.