A State Department spokeswoman said Sunday there were five Americans among the injured, but none among the dead.
"Obviously it's an enormous offense against everybody's sense of right and wrong," said Secretary of State John Kerry. "It represents the seriousness and the breadth of the challenge we face with ruthless and completely reckless terrorists, and we're going to pursue them."
The U.S. Embassy asked personnel to stay in place Sunday and avoid the Westgate Mall area and any large gatherings. All U.S. citizens in Kenya were urged to register online so the embassy can provide them with updated information on travel and security -- and can contact them in case of emergency.
Israel's Foreign Ministry said one national was slightly wounded and three escaped. A cafe at the mall is owned by an Israeli, but the ministry does not believe the mall was targeted because of that.
The Ghana president's office said literary figure Kofi Awoonor was among those killed in the attack.
"Such a sad twist of fate to place Prof at the wrong place at the wrong time," President John Mahama said in a statement.