But Sami al-Askari, the government adviser who announced the investigation into the film, said the opposition were using it to deflect attention from Saddam's crimes.
He told Iraqi state television: "They cannot say this court has been unjust and so they take this mistake and forget Saddam deserved to be executed. Saddam was treated well in court and on the scaffold."
He said: "No one beat him or insulted him, yet Saddam tortured many Iraqis, executed thousands and buried them in mass graves."
The film, apparently taken with a mobile phone, showed Saddam at his execution on Saturday being taunted by witnesses, including one who shouted the name of Moqtada al-Sadr, a Shia cleric.
The footage shows Saddam dying while the crowd shouts and ends with a close up of Saddam face, his neck broken, having fallen though the trapdoor of the gallows.
The video is more graphic than the brief clip released, without sound, on state television and quickly spread on the internet and between mobile phones.
Many Sunnis have been angered by the suggestion that someone in the party executing Saddam should be a Sadr supporter.
Sami al-Askari, a Shia politician who witnessed the execution, said it was one of the masked guards who shouted al-Sadr's name.
"All of us were suprised. It was a terrible act," he said.
"It will give a negative image of what's going on. We wanted to be careful and do everything according to the law, and then at the last minute this happened, one of the unreasonable guards started shouting bad things."
But another official present challenged government claims that those who filmed the event were guards, saying the chanting came from senior officials.
"One of the unreasonable guards started shouting bad things"
Munkith al-Faroon, a court official for the prosecution who can be heard appealing for order in the internet video, said he threatened to leave the room beause of the jeering, knowing that hanging could not proceed if he, as the prosecutions observer, was not present.
"I threatened to leave," said Faroon. "They knew that if I left, the execution could not go ahead."
A number of commentators have said the footage makes the execution look like a "sectarian lynching" rather than an act of law.
The execution has also been criticised for having taken place during the Muslim holiday of Eid Al-Adha, traditionally a time of forgiveness.
Iraqi officials have said Saddam died before sunrise and the official start of the four-day festival.
Saddam's execution had provoked protests in countries around the world, as well as in Iraq.
|Saddam's execution has provoked |
protests around the world [AFP]
In Tikrit, thousands continued to gather in specially-erected condolence tents and in Al-Dawr, where Saddam was captured by US forces in 2003, locals unveiled a huge marble portrait of Saddam.
Yahiya al-Attawi, a representative of the Muslim Scholars Association which conducted a mourning ceremony for Saddam, said: "We can't render to Saddam Hussein what he did for us, even if we did everything in our power."
In London, the video of Saddam's execution was condemned as "deplorable" by John Prescott, Britain's deputy prime minister.
"Frankly, to get this kind of recorded messages coming out is totally unacceptable and I think whoever is involved and responsible for it should be ashamed of themselves," Prescott said on BBC radio.