The US military also said for the first time it believes the three missing soldiers were abducted by al-Qaida-linked militants after an attack that included three roadside bombs.

"What you are doing in searching for your soldiers will lead to nothing but exhaustion and headaches. Your soldiers are in our hands. If you want their safety, do not look for them," the Islamic State of Iraq said on a militant Web site.

"You should remember what you have done to our sister Abeer in the same area," the statement said, referring to five American soldiers who were charged in the rape and killing of 14-year-old Abeer Qassim al-Janabi and the killings of her parents and her younger sister last year.

Three soldiers have pleaded guilty in the case one of the most shocking atrocities committed by U.S. troops in the Iraq war.

Three U.S. soldiers have been missing since Saturday, since a deadly attack on their convoy in Mahmoudiya, about 20 miles south of Baghdad. The attack also killed four U.S. soldiers and an Iraqi soldier, according to the military, which had described the Iraqi as an interpreter.

On Sunday, the Islamic State of Iraq claimed that it had captured U.S soldiers in the deadly attack in the Sunni area, which is known as the "triangle of death" and is an al-Qaida stronghold.

If the claim proves true, it would mark one of the most brazen attacks by the Islamic State of Iraq, a coalition of eight insurgent groups, including al-Qaida in Iraq.

About 4,000 U.S. troops backed by aircraft, intelligence units and Iraqi forces have been scouring the farming area around Mahmoudiya and the nearby town of Youssifiyah for three days, as the military promised to make every effort available to find the missing soldiers.

On Monday, U.S. military spokesman Maj. Gen. William B. Caldwell, IV said: "At this time, we believe they (the three soldiers) were abducted by terrorists belonging to al Qaida or an affiliated group, and this assessment is based on highly credible intelligence information."