Saddam Hussein's cousin Ali Hassan al-Majid or 'Chemical Ali' was executed on Monday, an Iraqi government official said, a week after he received a fourth death sentence.
"The condemned Ali Hassan al-Majid has been executed by hanging until death today," said spokesman Ali al-Dabbagh in a statement.
He was hanged after being convicted on 13 counts of killings and genocide, al-Dabagh said.
Majid was sentenced to death in four separate trials, including the one in which he was convicted for his involvement in a poison gas attack on the northeastern town of Halabja against Iraqi Kurds that killed about 5,000 people.
Most of the victims of the attack had been women and children, and is considered as one of the deadliest gas attacks carried out against civilians.
The 1988 poison gas attack, which earned Majeed his nickname 'Chemical Ali', was part of the Anfal campaign in which the Saddam Hussein regime killed at least 100,000 Iraqi Kurds.
While delivering his death verdict on January 17 on Majid, Judge Abud Mustapha al-Hamani termed the offences as "deliberate murder, a crime against humanity".
"Al hamdulillah, Al hamdulillah (praise be to God)," said a stone-faced Majid, at a hearing broadcast on television.
Majeed was sentenced to death also for his role in putting down a Shiite uprising against Hussein in 1991, and for his part in putting down a Baghdad revolt in 1999.Majid's execution was delayed due to legal wrangling.