Ali Hassan al-Majid was better known by his macabre nickname and as the King of Spades in the pack of cards of "most wanted" Iraqis issued by the US military in 2003, and will forever be associated with mass killings.
He was "executed by hanging until death," government spokesman Ali al-Dabbagh said. "The execution happened without any violations, shouting or cries of joy," in sharp contrast to Saddam's death on the gallows, he added.
State television later aired two still photographs of Majid, showing him wearing an orange-red jumpsuit and the first of which clearly displayed his face.
The second picture showed him on a platform, with a black hood over his head and with two men wearing balaclavas standing on either side.
The execution, which was welcomed by Kurdish victims, came as three massive car bombs targeting hotels rocked central Baghdad, killing at least 36 people and wounding 71 in an apparently coordinated but as yet unclaimed attack.
Majid was sentenced to death on January 17 for ordering the gassing of Kurds in the northeastern town of Halabja which killed an estimated 5,000 people and was one of the worst crimes committed by Saddam's iron-fisted regime.
"I was happy to see the news of the execution on television," said Kamal Abdelkadir, 24, who lost his parents, five sisters and a brother in the atrocity and who continues to require medical treatment for his injuries.
Fadhel Rifat, 27, who now lives in Sulaimaniyah, the eponymous Kurdish province in which Halabja is situated, was also just a young boy at the time of the attack.
"My father and many relatives died because of Chemical Ali," he said. "I am happy that he is dead."
Three-quarters of the victims at Halabja, whose crumpled bodies were shown in television broadcasts to an appalled world, were women and children in what is thought to have been the deadliest ever gas attack against civilians.
His conviction for the gas attack, that came as the Iran-Iraq war drew to a close, was the fourth time that Majid, who was arrested in August 2003, had received a death sentence.
Handing down the ruling, Judge Abud Mustapha al-Hamani branded Majid's offences as "deliberate murder, a crime against humanity" when the verdict was delivered amid muffled applause in the courtroom.
Prime Minister Nuri al-Maliki said Majid's execution was warranted as he was "one of the worst henchmen of the former regime, who committed heinous crimes against the Iraqi people".
"His name is associated with the mass graves that fill Iraqi land from north to south," Maliki said. "This turns another dark page in the genocide, repression and crimes against humanity committed by Saddam and his agents."
Majid's execution had previously been held up by legal wrangling. It had first been due to be carried out by October 2007 but was delayed so as not to coincide with the Muslim holy month of Ramadan.
Saddam -- Majid's close cousin -- was himself hanged in December 2006 for the killing of 148 Shiite villagers after an attempt on his life in 1982.
In contrast with Majid's hanging, however, footage of that execution posted on the Internet showed shouts of applause and barracking of the dictator both before and as he died.
Majid earned his moniker for ordering poisonous gas attacks in a brutal scorched-earth campaign of bombings and mass deportations that killed an estimated 182,000 Kurds in the 1980s.
He had already been sentenced to hang for genocide over the Kurdish offensives when in December 2008 he received a second death sentence for war crimes committed during the ill-fated 1991 Shiite uprising in southern Iraq.
Last March, the Iraqi High Tribunal handed down a third death sentence over the 1999 murders of dozens of Shiites in the Sadr City district of Baghdad and in the central shrine city of Najaf.
Majid orchestrated the Halabja attack when in March 1988, Iraqi jets swooped over the small town and for five hours sprayed it with a deadly cocktail of mustard gas and the nerve agents Tabun, Sarin and VX.
Considered Saddam's right-hand man and bearing a strong resemblance to the former dictator, he was a member of the decision-making Revolutionary Command Council and was regularly called upon to crush rebellion.
Two other Saddam cohorts -- former defence minister Sultan Hashim al-Tai and ex-army deputy operations chief Hussein Rashid al-Tikriti -- were ordered to hang for the brutal 1988 offensives known as Anfal but they remain in custody.
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