WASHINGTON (AFP) - A coalition air strike killed an Islamic State in Iraq and Syria (ISIS) finance chief in Iraq last month, the US military said on Thursday (Dec 10), hailing it as another scalp in its bid to blow apart the extremists' financial network.

Abu Saleh was killed in late November, US military spokesman Colonel Steve Warren said in a videoconference from Baghdad, calling him "one of the most senior and experienced members" of the group's nefarious financial system.

"Abu Saleh was the third member of the finance network that we have killed" recently, Warren added, likening him to a finance minister for the extremist group, which grabbed swathes of Iraq and Syria in a brutal offensive of beheadings and forced religious conversions.

Abu Saleh was killed along with two associates as part of the US-led coalition's campaign to destroy the extremists' financial infrastructure, Brett McGurk, Washington's envoy for the anti-ISIS fight, said on Twitter.

Real name Muwaffaq Mustafa Muhammad al-Karmush, the US State Department's terrorist blacklist describes him as a 42-year-old Iraqi.

"Killing him and his predecessors exhausts the knowledge and talent needed to coordinate funding within the organization," Warren said, adding that two other henchmen in ISIS fundraising networks also were killed in coalition air strikes in Iraq in late November.

They were identified as Abu Mariam, an enforcer and senior leader in ISIS group extortion networks, and Abu Rahman Al-Tunisi, who Warren said coordinated ISIS' transfer of people, weapons and information.

Abu Mariam appears on the State Department terrorist list as Mounir Ben Dhaou Ben Brahim Ben Helal, a 32-year-old Tunisian.

"These strikes are an example of how we are able to decimate networks," Warren said.

The coalition has been targeting ISIS leaders in Syria and Iraq with air strikes to try to pick apart its command structure.

After the attacks in Paris last month, the United States said it was deploying a special operations unit in Iraq that will be able to mount raids into Syria to capture or kill ISIS leaders.

"We want this expeditionary targeting force to make ISIL and its leaders wonder when they go to bed at night: who's going to be coming in the window," US Defense Secretary Ashton Carter told a Senate hearing, referring to another name for the group.

In London, the US Treasury's acting undersecretary for terrorism and financial crimes, Adam Szubin, said the ISIS group derives most of its funding from economic activity in the territory it controls and has declared a caliphate.

It has reaped more than US$500 million (S$705 million) in black market oil sales, looted bank vaults captured in Iraq and Syria, and raised millions more through extortion.

But to run what amounts to a mini-state, it needs steady and renewable sources of funding, and to do that it needs access to the international financial system to move money and import supplies, according to Szubin.

"We are targeting both of these dependencies - ISIL's ability to generate revenue and its ability to use that revenue," he said in a speech to the Chatham House think tank.

"Most recently, the coalition launched a military campaign - Tidal Wave 2 - which included precision strikes against ISIL's key energy assets: oil fields, refineries, and tanker trucks.

"We believe these air strikes are markedly degrading one of ISIL's most important sources of funding," he said.