"They're just seeing dead bodies. They've found no survivors, no live hostages," said a Nairobi resident whose brother was taking part in the military sweep inside the mall.
Kenyatta said 11 suspects had been arrested; authorities previously announced that seven had been taken into custody at the airport and three elsewhere.
"These cowards will meet justice as will their accomplices and patrons, wherever they are," an emotional Kenyatta declared.
"We confronted this evil without flinching, contained our deep grief and pain, and conquered it," he said. "As a nation, our head is bloodied, but unbowed."