Al-Qaeda's supporters in Iraq have said they have captured several US soldiers after ambushing their patrol south of Baghdad. The Islamic State in Iraq, which works closely with al-Qaeda, said in a statement posted on a website on Sunday that its fighters had captured the soldiers - it did not say how many - in an attack on Saturday.

"God has enabled your brothers at the Islamic State in Iraq on Saturday ... to clash with a crusader patrol in Mahmudiya area at the southern part of Baghdad," the statement said. "Some were detained and some were killed.

"We will provide the full details of this blessed operation as soon as they are available." The US military said that three of its soldiers were missing after their patrol was ambushed in Mahmudiya on Saturday.

Military spokesmen in Baghdad also said that an additional five soldiers had been confirmed killed in the attack.

US-led troops backed by helicopters and jets have reportedly launched an extensive hunt for the missing personnel; combing orchards, searching farms and setting up roadblocks west of Mahmudiya.

"We will make every effort available to find our three missing soldiers," Major-General William Caldwell, the chief spokesman for the US military in Iraq, said.

Residents said the patrol was ambushed after it struck a roadside bomb on a rural road in an area of palm groves called Shibaiya, near the town of Yusufiya.

Last June, followers of al-Qaeda captured two US soldiers at a checkpoint in Yusufiya.

Their mutilated and booby-trapped bodies were found days later after a search by thousands of troops.