The Iraqi High Tribunal -- set up to try former regime officials -- will pass judgement on the accused for the brutal military campaign known as Anfal in northern Iraq in which nearly 3,000 villages were razed to the ground.

The sentencing hearing opened with chief Judge Mohammed al-Oreibi al-Khalifah calling on the six defendants one by one.

The most prominent defendant is Ali Hassan al-Majid, a cousin of Saddam who is widely known as "Chemical Ali" for allegedly ordering chemical gas strikes against Kurdish villages.

He faces a charge of genocide, while the five others are accused of war crimes and crimes against humanity, all charges that carry the death penalty.

The five are Sabir al-Duri, former director of military intelligence; Sultan Hashim al-Tai, a former defence minister; Hussein Rashid al-Tikriti, former armed forces deputy chief of operations; Farhan al-Juburi, a former military intelligence commander; and Taher al-Ani, former governor of the main northern city of Mosul.

Majid is the only individual besides Saddam to be charged with genocide over the Anfal (Spoils of War) campaign against the Kurds in the late 1980s when the Iran-Iraq war was at its peak.

Saddam, driven from power by a US-led invasion in April 2003, was executed last December 30 for crimes against humanity in a separate case.

Prosecutors have demanded the death penalty for five of the accused, but have asked the court to free Ani for lack of evidence.

Chief prosecutor Munquith al-Faroon has also personally requested a more lenient sentence for Duri.

Over the course of the trial, which opened on August 21 last year, a defiant Majid said he was right to order the attacks.

"I am the one who gave orders to the army to demolish villages and relocate the villagers," he said at one hearing. "The army was responsible to carry out those orders."

In a sometimes belligerent tone, Majid said he was not defending his actions. "I am not defending myself. I am not apologising. I did not make a mistake," he told chief judge Mohammed al-Oreibi al-Khalifah.

Since the execution of Saddam, Majid has emerged as the star defendant in the trial and takes the front seat in the dock previously occupied by the former dictator.

Ahead of the judgement, the defence team approached the United Nations chief Ban Ki-moon to stop the trial which it said was marred by "errors".

"I appeal to the UN Secretary General to quickly intervene and save the six accused from execution in the Anfal trial," lead defence lawyer Khalil al-Dulaimi said in a statement released in Amman.

"The six are prisoners of war and their trial by the Iraqi High Tribunal was marred by errors and violations of the law."

Human Rights Watch also expressed concern on Friday that the verdicts in the Anfal trial could be flawed as it said they were in the previous trial of Saddam over the killing of Shiites from the village of Dujail in the 1980s.

The analysis of the Dujail trial "shows serious flaws in the application of basic international criminal law principles," said Richard Dicker, who heads the watchdog's International Justice Programme.

"This raises concerns such errors will be repeated in the Anfal judgement and it therefore won't withstand scrutiny or the test of time."

The New York-based group said the Anfal trial has also been marred by procedural flaws, including the government's removal of the first presiding judge, Abdallah al-Ameri, a few weeks after the start of the trial.

In addition, Human Rights Watch "raised concerns about vague charges which made it difficult for the defendants to prepare their case and the inability of the defence to call witnesses who feared for their security."