The bodies, of men aged between 20 and 45-years-old, were reportedly victims of sectarian death squads. Their discovery is the highest daily figure since the end of the Muslim holy month of Ramadan.

Shia militiamen have been blamed for many of Baghdad's sectarian slayings, which have increased in number following the bombing of a Shia shrine in the city of Samarra in February. Since October 1 more than 1,300 Iraqis have been killed in the continuing violence.

The 56 bodies were wearing civilian clothes and had been bound at the wrists and ankles, police Lt Mohammed Khayon, told AP. He said the bodies showed signs of having been tortured.

At the same time the US military announced the deaths of three soldiers in Baghdad and a Marine in the western province of Anbar.

A brief statement said that the three soldiers had died yesterday when the vehicle they were travelling in was hit by a roadside bomb in eastern Baghdad. A separate announcement said one Marine died from injuries "due to enemy action" also yesterday.

Earlier US-led forces said that 13 suspected insurgents had been killed during a raid on a building in Mahmoudiya, about 20 miles south of Baghdad.

Five people were killed inside the building, including a man wearing an explosive vest, and eight were killed as they fled the area.

Iraq cancelled all military leave from today following growing fears of increasing violence on Sunday when the Iraqi High Tribunal trying Saddam for crimes against humanity will deliver its verdict.

Abdul-Qader al-Obeidi, Iraqi Defence Minister, was heard issuing the order in a video of a meeting between the Iraqi Prime Minister Nouri al-Maliki and senior military and security officials.

Meanwhile, John Negroponte, the US Director of National Intelligence, met Mr al-Maliki in Baghdad today for talks.

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