Senior officers were aware of the deaths but believed that it was because of sectarian violence, a US official said.

The military said that Major-General James D. Thurman, commander of the 4th Infantry Division, had ordered a criminal investigation into the alleged killing of a family of four in Mahmoudiyah, 20 miles (30km) south of Baghdad. An official close to the investigation said that the soldiers were assigned to the 502nd Infantry Regiment and that one of them had admitted his role in the incident and been arrested.

The official said that the suspects were from the same platoon as two soldiers whose mutilated bodies were discovered on June 19, three days after there were abducted by insurgents near Youssifiyah, southwest of Baghdad.

According to the official, the mutilation of the murdered troops stirred feelings of guilt and led at least one of the five suspects to reveal the rape-killing. (AP)

Times Recommends

• Michael Jackson: Not the final chapter
• Indian Army spends10m rupees on golf buggies
• Brüno toned down for 15 rating