Four American soldiers, one just newly arrived, were killed and another wounded in separate bomb attacks in Baghdad, a US military official said. A home made bomb exploded late Saturday night killing a least three soldiers and injuring a fourth as they patrolled an area in southeast Baghdad, the official said. A second bomb exploded at about 6:30 am on Sunday in Baghdad, injuring one soldier from the 1st Infantry Division, the official said. "The soldier was taken to the 31st Combat Hospital where he died," Military spokeswoman said. On Saturday morning, at least two US soldiers were killed and several wounded, some of them badly, in an attack on an army convoy in the centre of the northern city of Tikrit. **PHOTO CAPTION*** Iraqis walk past a crater created by an explosion in central Tikrit that killed two US soldiers while on patrol Saturday March 13, 2004, about 180 km northwest of Baghdad, Iraq. (AP Photo/Hadi Mizban)