Saddam's half-brother and former head of intelligence, Barzan Ibrahim al-Tikriti, and Awad Ahmed al-Bandar, the former chief judge of revolutionary court, will be hanged at dawn on Thursday, the official said.

"Their documents have been signed and they will be executed Thursday," he told AFP, speaking on condition of anonymity, adding that the pair remains for the time being in the custody of US authorities.

On November 5, the two were found guilty along with Saddam by an Iraqi court of ordering the massacre of 148 Shiites from Dujail village in the 1980s in revenge for an failed attempt on the then president's life.

Saddam was hanged on December 30 at a former torture centre in Baghdad's Shiite district of Kadhimiyah and buried a day later at his home village of Awja in northern Iraq.

Barzan and Bandar were to have been hanged along with Saddam, but their execution was later postponed as "we did not have time on that day," the official in Prime Minister Nuri al-Maliki's office said.

The Iraqi government wanted to complete Saddam's execution before sunrise, which marked the start of Eid al-Adha, one of Islam's holiest holidays and traditionally a time for forgiveness. The festival ends on Wednesday.

Hot-tempered and secretive, Barzan was one of Saddam's most trusted aides, while Bandar was the first judge to be tried for ordering executions since Nazi judges were brought before the Nuremberg trials after World War II.

Saddam's execution, meanwhile, has dramatically increased tension between Iraq's already feuding Sunni and Shiite communities, especially after a grisly video showing the Sunni leader taunted by Shiite hangmen surfaced.

On Tuesday, Maliki launched an inquiry into the source of the grainy yet graphic video, apparently taken with a mobile phone, which has enraged Sunni Arabs across Iraq and offended international leaders.

"He's very serious about this inquiry, and he wants to punish whoever is responsible," said a Shiite lawmaker with close links to the prime minister.

The unofficial footage shows Saddam taunted by Shiite guards shouting the name of radical Shiite cleric Moqtada al-Sadr -- making the execution look more like a sectarian lynching than a court-directed punishment.

It appeared on the Internet, and was exchanged between Iraqi mobile phones.

Sami al-Askari, a senior official who attended the execution, said Maliki had ordered a three-member panel of inquiry to find which of those present at the hanging had filmed the execution.

Interior Ministry spokesman Brigadier General Abdel Karim Khalaf said the committee was "working secretly and we can't give details (but) whoever is responsible for leaking the film will be punished."

On Tuesday, Munqith al-Faroon, the prosecutor who oversaw the execution, said on Al-Jazeera television there were only two people who had mobile phones inside the room. "They were senior government officials," he said.

Aside from Askari, who has denied filming, there were a handful of other officials present at the hanging, including National Security Adviser Mowaffaq al-Rubaie, who was not available for comment.

That someone in the party executing Saddam should be a Sadr supporter has angered Sunnis and has given a sectarian colour to the hanging of one of the most powerful Sunni Arab leaders.

The footage ends with Saddam -- convicted for crimes against humanity -- falling though the trapdoor of the gallows amid shouts from the crowd.

US military spokesman Major General William Caldwell said US forces handed "physical control" of Saddam to Iraqi officials shortly before the hanging, and all US personnel had left the Iraqi prison facility before it took place.