Four American soldiers were killed during combat in Baghdad, including three in a single roadside bombing, the US military said Friday. Three soldiers were killed and 11 wounded Thursday when a bomb exploded near their combat patrol in eastern Baghdad, the military said in a statement. Four of the wounded were treated and returned to duty, it said. Another soldier was killed and three wounded the same day during combat operations in a western section of the capital, an earlier statement said. The military did not release details of the incident.