Two American soldiers have been killed in separate attacks in Baghdad.
And at least one other soldier was injured when a US vehicle hit an explosive in part of the city believed to have been cleared of land mines.
In the first shooting attack, an unidentified Iraqi walked up to a soldier on a bridge and opened fire with a pistol, apparently at close range.
Senior US Army officers in Baghdad say the soldier, whom they did not identify, belonged to the 2nd Armoured Cavalry Regiment.
US forces say they trade fire with armed Iraqis almost daily across the country.
In a separate attack, a US Army 3rd Infantry Division soldier was killed when a sniper shot him in the head in east Baghdad, says Captain Tom Bryant, spokesman for the Army's V Corps, which is based at Baghdad's airport. He had no further details.