The occupation force said on Sunday the fatalities occurred near the northern Iraqi city of Kirkuk where US troops came under a rocket-propelled grenade attack. Another US solider was wounded in the attack.
The latest deaths brought to 103 the total number of Americans who have died in combat since US President George Bush announced the end of combat on 1 May.
US troops came under resistance attacks elsewhere in Iraq as well.
The Aljazeera correspondent quoted eyewitnesses seeing a rocket hit a US ammunition truck in the flashpoint town of Falluja, triggering a huge explosion and a blaze.
Iraqi gunmen then fired on the US troops caught off guard.
"I saw American casualties and gunmen fired on them," said a news agency photographer who was driving close to the convoy when the attack took place.
"American soldiers fired back," he added.
US soldiers also came under mortar attack near the city of Samara, about 120km north of Baghdad.
Our correspondent quoted locals as saying that US helicopters were flying over the area.