Ezzat Ibrahim al-Douri, former right-hand man to late Iraqi President Saddam Hussein and a leader of Iraq's Sunni insurgency, has been reported killed by Iraqi forces and Shi'ite militias.
Douri was killed in a military operation, Raed al-Jubouri, the governor of Salahuddin province, told Reuters. The pan-Arab television network al-Arabiya showed images of a dead man who looked like al-Douri.
Baghdad has mistakenly announced al-Douri's death several times before, but this time photos are circulating showing a man with features and red hair like his. Al-Jubouri told Reuters DNA from the body would be tested and results released "very soon".
His killing, if confirmed, would be a big blow to the Sunni insurgency, an alliance of former Baathist officers and Islamic State.
"The mastermind of terrorist operations has been killed and he is Ezzat al-Douri," al-Jubouri told Arabiya TV. "al-Douri is the biggest mastermind behind all attacks that undermined Iraq. This news will have an impact on the morale of the fighters."
After the 2003 invasion, he was ranked sixth on the US military's list of 55 most wanted Iraqis and a $10 million reward was offered for his capture. US officials accused him of organizing the insurgency that peaked in 2005-07.
The mere sight of Douri, a wiry man with a red mustache who often wore a military beret, terrified Iraqis who endured what was known as the Republic of Fear.
After Douri's long absence, Iraqis suddenly heard what appeared to be the voice of a man who played a role in many of the worst atrocities against Shi'ites, Kurds and Sunnis.
This time Douri seemed to be on the side of Islamic State, and he praised the Sunni militants who seized large parts of the country and eventually declared a caliphate.
Although elderly and reported to have been in poor health, Douri was believed to be the leader of the Baathist militant group the Naqshbandi Army, one of several groups said to have supported Islamic State.
"Join the ranks of the rebels who liberated half the country," said the voice on the recording, which resembled previous tapes released in Douri's name.
"The liberation of Baghdad is around the corner. Everyone should contribute, to the extent of his ability, to complete the liberation of the beloved country, because there is no honor or dignity without its liberation."
Douri has been described as the mastermind of the insurgency against the Shi'ite-led government. But no solid evidence of that has emerged and there were also signs that the alliance of convenience was short-lived.
An intelligence official in the interior ministry said he believed Baathists, including Douri, had provided funding to Islamic State, but had ultimately been superseded by the radical jihadists.
"In the beginning of 2014 and since military councils (Baathists) and Daesh (Islamic State) had a temporary marriage. It was a one night stand," he said.
"The Baathists thought they could use Daesh to reach Baghdad, but the radicals used the Baathists to be acceptable and win over the people."
Karim al-Nouri, a leader in the Badr organization and spokesman for Shi'ite militias fighting Islamic State, said his forces had been involved in the operation although they thought the target was the leader of Islamic State, Abu Bakr al-Baghdadi.
"We received intelligence from our sources that a VIP was in the city of Hawija and we were waiting to ambush him. Based on our intelligence, it was believed that the man was al-Baghdadi, but it turned out to be al-Douri."
"He was the second man after Saddam Hussein and was the coordinator between the Baath party and IS. The body is now taken for identification, but we are certain it is al-Douri," al-Nouri added.
Khdhayer Almurshidy, an exiled spokesman for Iraq's former Baath party, said in comments to Iraq's al-Hadath TV that the reports of al-Douri's death were false.
Al-Jubouri however told Reuters that "a group of security forces went and surrounded an area and those terrorists were killed. Three of them were suicide bombers and blew themselves up. Amongst the bodies was Douri's."
Douri was one of the main plotters of the coup that brought the Baath Party to power in 1968. He quickly rose through its ranks.
In 1998, he escaped an assassination attempt in the city of Kerbala, home to may of the majority Shi'ites he repressed.
Jubouri described the operation as "a major victory and a strike against the terrorists", referring to Islamic State, a hardline Sunni Muslim offshoot of al Qaeda which has taken swathes of Syria and Iraq and proclaimed a caliphate.