Five American soldiers have been killed in Iraq, including four in a single incident, the US military said Sunday. A roadside bomb killed four soldiers Saturday while they were on patrol in western Baghdad, the military in a statement. Small arms fire followed the blast, wounding another soldier. The attack occurred as the soldiers were conducting patrols as part of a month-old security operation to end sectarian violence in the capital, the statement said. Another soldier died the same day in a non-combat related incident, the military said in a second statement. The circumstances were under investigation, it said.