A top Iraqi court has confirmed the death sentence on "Chemical Ali" and two other cohorts of Saddam Hussein convicted of genocide and crimes against humanity, a senior judge said on Tuesday.

"The Iraqi supreme court has confirmed the death sentence on Ali Hassan al-Majid, Sultan Hashim al-Tai and Hussein Rashid al-Tikriti," the court head judge Aref Shaheen told a press conference.

Majid, widely known as "Chemical Ali," was the executed Iraqi dictator's most notorious hatchet man, Tai was his defense minister and Tikriti was armed forces deputy chief of operations.

The three were sentenced to death on June 24 after being found responsible for the slaughter of thousands of ethnic Kurds in the so-called Anfal campaign of 1988.

They will be hanged within 30 days in line with Iraqi law.

An estimated 182,000 Kurds were killed and 4,000 villages wiped out in the brutal campaign of bombings, mass deportation and gas attacks known as Anfal.

"Thousands of people were killed, displaced and disappeared," Iraqi High Tribunal Chief Judge Mohammed al-Oreibi al-Khalifah said after he had passed sentence in June.

"They were civilians with no weapons and nothing to do with war."