Reuters television footage from Baghdad's Yarmouk Hospital showed three men and two boys who had been wounded in the attack, doctors had amputated the left leg of one of the boys.
A medic at the hospital said the dead included seven men, two women and four children.
The US military said it estimated two or three people were killed or wounded but could not give a precise figure as the bodies were removed before troops arrived at the scene.
Leighton said: "We regret when civilians are hurt or killed while coalition forces search to rid Iraq of terrorism. Terrorists continue to deliberately place innocent Iraqi women and children in danger by their actions and presence."
In a separate development, police said on Saturday that a mortar shell killed Abdul Khaliq Nasser, an Iraqi journalist in the northern city of Mosul, bringing to four the number of local media workers killed this month.
Nasser, who reported for a newspaper in the city, was killed outside his house in the western Bab al-Bayd area when the artillery round landed nearby late on Friday.