Enraged crowds protested the hanging of Saddam Hussein across Iraq's Sunni Muslim heartland Monday, as the government launched an inquiry into how guards filmed and taunted the deposed president as he stood on the gallows.

A mob in Samara broke the locks off the Golden Dome, a bomb-damaged Shiite Muslim shrine, and marched through while carrying a mock coffin and photo of Saddam.

Until Saddam's execution Saturday, most Sunnis sympathized with militants. But they avoided taking a direct role in the sectarian conflict in spite of attacks by Shiite militia that have killed thousands of Sunnis or driven them from their homes.

Monday's demonstration at the shrine could suggest many Sunnis may now more actively back the small number of militants fighting against Iraq's Shiite-dominated government. The Feb. 22 bombing of the shrine by Sunni extremists is widely seen as the trigger for the current cycle of tit-for-tat attacks between Sunnis and Shiites.

Many Sunnis, already outraged by Saddam's hurried execution which happened just four days after a court upheld his conviction and sentence, were angered by news of the unruly scene in the execution chamber.

Saddam's execution was captured on video, in which the former dictator was taunted with chants of " Muqtada, Muqtada, Muqtada" -- referring to Muqtada al-Sadr, a Shiite cleric who controls one of Iraq's most violent religious militias. Al-Sadr is also a major power behind the government of Shiite Prime Minister Nouri al-Maliki.

Reuters news agency reports the Iraqi government launched an inquiry Monday into how guards filmed and taunted Saddam on the gallows, turning his execution into a spectacle.

Video was released by the Iraqi government showing a hangman talking to a composed Saddam as he placed the noose around his neck.

But footage recorded on a mobile phone and circulated on the Internet showed guards shouting "Go to hell," chanting Muqtada and trading insults with Saddam before the metal trap door below him opened while he was in mid-prayer. His body swung, his neck clearly broken, as he hung on the rope.

A senior Iraqi official told Reuters the U.S. ambassador tried to persuade al-Maliki not to rush into hanging the former president just four days after his appeal was turned down, urging the government to wait another two weeks.

In a Sunni neighbourhood in northern Baghdad, hundreds of demonstrators mourned the executed Saddam. Some praised Saddam's Baath Arab Socialist party.

"The Baath party and Baathists still exist in Iraq and nobody can marginalize it," Samir al-Obaidi, 48, who attended a Saddam memorial in the Azamiyah neighbourhood, told AP.

In Dor, 124 kilometres north of Baghdad, hundreds more took to the streets to attend the dedication of a giant mosaic of Saddam. Children carried toy guns while men fired their weapons into the air.

Meanwhile, mourners at a mosque in Saddam's hometown of Tikrit slaughtered sheep as a sacrifice for their former leader. The mosque's walls were lined with condolence cards from tribes in southern Iraq and Jordan who were unable to travel to the memorial.

U.S. deaths top 3,000

In the midst of these protests, U.S. forces continued operations in Iraq.

Six Iraqis were killed in a U.S.-led raid on the Baghdad offices of a top Sunni politician, Saleh al-Mutlaq. The U.S. military and Iraqi police said they suspected the offices were being used as an al Qaeda safe house.

The U.S. death toll, meanwhile, climbed to at least 3,002 by the final day of 2006 as the military reported the deaths of two more soldiers in an explosion Sunday in Diyala Province, northeast of the capital. With the announcement, the Associated Press count of fatalities showed at least 113 U.S. service members died in December. That makes it the bloodiest month of 2006.

With files from The Associated Press