Sergeant Brent Williams of the 1st Armoured Division said the blast had probably been caused by a landmine. US forces regularly come under attack on the same road, which leads to a US base.
A crowd of children gathered at the scene, throwing stones at occupation forces and shouting their support for ousted Iraqi President Saddam Hussein.
Daily resistance attacks against US forces have killed 53 soldiers since Washington declared an end to major hostilities on 1 May.
US occupation officials have admitted resistance attacks are increasingly sophisticated and deadly.
US occupying administrator for Iraq Paul Bremer said on Saturday that killing of Hussein’s sons Uday and Qusay would undermine the resistance campaign. But since their death last month attacks have not abated.
Residents say they will not visit
Two Iraqi flags covering the earthen graves of Hussein’s sons were stolen overnight, despite American troops guarding the cemetery in the fallen leader’s birthplace of Awja village on the edge of Tikrit.
Residents of the area criticised the continued US presence and said they would not visit the plot as long as foreign troops guarded it. Occupation forces fear the grave site could become a rallying point for Hussein loyalists.
Some local residents accused US troops of stealing the flags.
US helicopters transported the corpses of Uday and Qusay along with the latter’s 14-year-old son Mustapha to Tikrit, 175 km north of Baghdad, on Saturday morning before being transferred to Awja.
The leading cleric in Hussein’s hometown cancelled a memorial service for the dead sons under pressure from the chief of the ousted leader’s tribe.
A memorial service was scheduled for Monday but Hussein’s family backed down in what is believed to be a condition imposed by the Americans for the dead to be buried in Awja.
Occupation soldiers continued their sweep for Hussein on Sunday near Balad, 60 km north of Baghdad, detaining 10 people.
Last week US forces said they had detained more than 700 Iraqis.