The second-in-command of the Islamic State of Iraq and the Levant group was killed during a US air strike in Iraq on Tuesday, according to the White House.
The US and its allies stage daily air strikes on ISIL targets in the group's self-declared caliphate based in Iraq and Syria.
A drone strike last month killed a senior leader in its Syrian stronghold of Raqqa.
"Fadhil Ahmad al-Hayali, also known as Hajji Mutazz ... was killed in a US military air strike on August 18 while travelling in a vehicle near Mosul, Iraq, along with an ISIL media operative known as Abu Abdullah," Ned Price, White House spokesman, said in a statement.
"[His] death will adversely impact ISIL's operations given that his influence spanned ISIL's finance, media, operations, and logistics."
Speaking to Al Jazeera from Washington DC, Joshua Walker, a former adviser to the US State Department and a Nonresident Transatlantic Fellow at the German Mashall Fund of the United States, said: "Nobody knows how many [ISIL] deputies there are.
"There's only one top man [Abu Bakr] al-Baghdadi and he's got a price on his head."
The White House said Hayali was a "primary coordinator" for moving weapons, explosives, vehicles, and people between Iraq and Syria.
He was in charge of operations in Iraq and helped plan the group's offensive in Mosul in June of last year, the White House said.
Mutazz was a lieutenant-colonel in the army of deposed leader Saddam Hussein and, like many who later went on to form the core of ISIL's leadership, was detained by US troops in Iraq at the Camp Bucca detention facility, according to US counterterrorism experts.
Al Jazeera's Zeina Khodr, speaking from Baghdad, said: "Iraqis who have contacts inside Mosul are saying their contacts informed them that ISIL did indeed lose a high-ranking member but they cannot confirm who.
"If it is confirmed he has been killed, it would be a blow to the organistion."
In December last year, General Martin Dempsey, chairman of the US joint chiefs of staff, told the Wall Street Journal newspaper that three members of ISIL's "senior leadership" had been killed.
Following these remarks, it was widely reported that Hayali was among the dead.
Asked about these reports on Friday, Dempsey's press office told Al Jazeera he had only referred to "senior leadership", and that particular individuals had only been named by others, not Dempsey.
For his part, Walker, the former State Department adviser, told Al Jazeera: "In terms of ISIL's operational capabilities, [Hayali's killing] is clearly a blow.
"It's obviously part of a larger war in terms of being able to win the hearts and mind of people that live in this region, to be able to give confidence in the US [and] the coalition's ability to defeat ISIL."
Nevertheless, he cautioned: "I think that the long-term strategy is to be determined.
"I think the challenge has been who are we backing on the ground. There's a larger issue here on having a regional solution and having all the regional players on the same page."
|The White House said Hajji Mutazz was in charge of operations in Iraq and helped plan last June's Mosul offensive [AP]
Source: Al Jazeera and agencies