"These terrorists chose to deliberately place innocent Iraqi women and children in danger by their actions and presence."
US aircraft attacked an area in the Lake Thar Thar region, 120km north of Baghdad, after intelligence reports indicated al-Qaeda members were there, the US military said.
Four fighters were killed during the first raid and the suspects at the scene then moved to another area south of the lake.
US forces came under small arms fire from a building, the US military statement said.
"Responding in self-defence, supporting aircraft engaged the enemy threat," the statement said.
"After securing the area, the ground force assessed 15 terrorists, six women and nine children were killed. Two suspects, one woman and three children were wounded and one suspected terrorist was detained."
George Bush, the US president, ordered 30,000 additional troops to Iraq in June in an attempt to stem sectarian violence between Sunni and Shia Muslims.
Thursday's news of the raid comes just days after another raid by US forces on Khalis, a Shia city north of Baghdad, led to the deaths of 25 people.
US troops called in air raids after meeting resistance while hunting suspected arms traffickers from Iran to Baghdad, but village leaders said those killed included civilians.