Kenyan security forces are continuing to work to apprehend gunmen who killed at least 59 people and wounded 175 others at a busy shopping mall in Nairobi.
Officials said the operation to capture the gunmen and rescue an unknown number of hostages was still ongoing midday Sunday inside the Westgate Mall, about 24 hours after the attack began.
Interior Secretary Joseph Ole Lenku said more than 1,000 people have been evacuated from the mall so far, calling the situation "very fragile."
He said officials believe there are between 10 and 15 attackers involved and he vowed that they will face the full force of the law.
The Somali terrorist group al-Shabab has claimed responsibility for the attack, saying it is retaliation for Kenya's military intervention in Somalia. An al-Shabab spokesman said in an audio message, "Either leave our country or live with constant attacks."
Kenyan forces entered Somalia two years ago to fight al-Shabab militants who had often crossed the border to stage attacks.
The U.N. Security Council and Secretary-General Ban Ki-moon strongly condemned the attack. Mr. Ban called it a "premeditated" and "totally reprehensible" act targeting defenseless civilians.
Witnesses said the gunmen wore masks and tossed hand grenades at the Westgate Mall during busy shopping hours. Children were among the wounded.
Kenyan President Uhuru Kenyatta sought to reassure shaken Kenyans in an address to the nation just hours after the attack. The president condemned what he called the cowardly act and praised Kenyans for their solidarity in the face of the terrorist threat.
The president said, "Terrorism in and of itself is the philosophy of cowards. The way we lead our lives in freedom, unity and consideration for each other represents our victory over those who wish us ill."
President Kenyatta vowed that the perpetrators will be caught and dealt with. He said the government stands ready to defend the country from within and from outside.
Canada and France each say two of their citizens were killed. The United States says no Americans were killed, but that some have been injured. Secretary of State John Kerry condemned the attack and said the United States has offered Kenya's government its full support to help bring the perpetrators of the attack to justice.