The explosion occurred overnight while the soldiers were conducting a combat patrol in the northern part of Baghdad.
In the restive western province of Al-Anbar, 18 people were injured when U.S. Marine helicopter made a hard landing while on a routine passenger and cargo flight. The military said enemy action did not appear to be the cause of the incident.
News agencies say that more than 2,900 U.S. servicemen have now been killed in Iraq since the war began in March 2003.
In other incidents, two Iraqis were reported killed and 14 were wounded in three explosions in the capital.
In a village near the northern city of Kirkuk, police say unidentified militants stormed a house belonging to a Turkmen Shi'ite family and killed four of its members.
(dpa, AP, AFP)