Kenya's president: Three floors of the Westgate Mall collapsed during siege

Kenya's president announced Tuesday that a siege of a Nairobi shopping mall was over, but said losses from the attack by Islamist gunmen were "immense" and at least 67 people had died.

"We have ashamed and defeated our attackers, that part of our task is completed," President Uhuru Kenyatta said in a televised address to the nation.

"Our losses are immense," he said. "We have been badly hurt, but we have been brave, united and strong. Kenya has stared down evil and triumphed. We have defeated our enemies and showed the whole world what we can accomplish."

Kenyatta said 61 civilians and six members of the security forces died in the siege. He said five attackers had been killed and that there were 11 suspects in custody.

The toll was provisional, he indicated, saying "three floors of the mall collapsed, trapping several bodies within the rubble including those of terrorists."

The president also called three days of national mourning.

A group of attackers marched into the four-storey Westgate Mall at midday Saturday, spraying shoppers with automatic weapons fire and tossing grenades.

Somalia's Al Qaeda-linked Shebab said it carried out the attack.

Kenyatta said "intelligence reports had suggested that a British woman and two or three American citizens may have been involved in the attack."

"We cannot confirm the details at present but forensic experts are working to ascertain the nationalities of the terrorists."

The president promised "full accountability for the mindless destruction, deaths, pain, loss and suffering we have all undergone."

"These cowards will meet justice, as will their accomplices and patrons, wherever they are."