An email sent to a Western news agency and signed by the Arab Socialist Baath Party - Iraq Command, said al-Duri died shortly before 2.30am on Friday but gave no indication of the cause.
"The leader of the resistance died on Friday 11 November at 2.20am," according to the statement signed by the Baath command.
There was a $10 million US bounty outstanding on al-Duri, who was said to be gravely ill with leukaemia. He was erroneously reported to have been captured in September 2004.
He was the most senior former Iraqi leader still at large since Saddam was captured in December 2003 from a hole in the ground on a farm.
Arab satellite television stations broadcast the report based on the email but said they had no independent confirmation. US and Iraqi officials in Iraq also said they were aware of the report but could not verify it.
Abd al-Rahman Muhammad Ibrahim, nephew and son-in-law of al-Duri, said he had heard the report on an Arab satellite television station but had no independent confirmation.
"We don't have such news," he said. "I cannot deny or confirm the report."
In Amman, Jordan, the secretary-general of the Jordanian Baath wing, Taysir al-Humsi, also said he had no information except what he had seen on television.
Born in 1942, al-Duri was considered to be the right-hand man of Saddam and he held a prominent position in the Baath government.
A top military commander, he played a key role in using chemical weapons against Kurdish civilians, and he also surpervised tribunals charged with repressing a Shia uprising in southwestern Iraq in 1991.
Al-Duri was suspected of being behind several guerrilla attacks against US occupation forces, as well as allegedly brokering an alliance between pro-Baathist fighters and Islamists in Iraq.
Izzat Ibrahim al-Duri, (L) with
former president Saddam Hussein
Al-Duri had been rumored to be suffering from a serious illness, possibly leukaemia, before Saddam's government fell. He sought medical treatment in Austria in 1999 but had to leave abruptly after human rights groups threatened to file charges against him in Austrian courts.
Last June, the Iraqi government said in a statement that al-Duri was sick and losing influence among Baath party leaders but none the less retained his ability to "recruit terrorists and finance terrorist attacks with money he stole from Iraq and transferred to Syria during the rule of the tyrant Saddam".
Al-Duri had been rumoured to have been arrested several times before, most notably in September 2004, when the Iraqi authorities announced his capture during a raid near his home village near Tikrit. Later, the Iraqi Defence Ministry said the report was false.