Jaburi, also the suspected former deputy to the late IS leader Abu Bakr al-Baghdadi, was arrested "in Turkey", a senior Iraqi military source told AFP without elaborating.

Prime Minister Mustafa al-Kadhemi had earlier announced on Twitter that Jaburi was arrested by the intelligence services "outside the borders" of Iraq, in a "complex external operation," without naming the location.

It was not immediately clear if Turkish authorities were involved and there was no immediate reaction from Ankara.

The US had offered a reward of up to $5 million for the capture of Jaburi.

The US Rewards for Justice programme said Jaburi had "reportedly served as the equivalent of... finance minister (for IS), supervising the group's revenue-generating operations from illicit sales of oil, gas, antiquities and minerals".

In September 2015, the US Treasury Department labelled Jaburi as a Specially Designated Global Terrorist.

IS took over one third of Iraq in a lightning offensive in 2014, expanding their self-declared "caliphate" stretching across the Syrian border.

Iraq's government declared victory against the jihadists in late 2017 after a grinding military campaign backed by a US-led military coalition.

Baghdadi was killed in a raid by US special forces in northwestern Syria in October 2019.

IS sleeper cells still periodically launch attacks in Iraq, against both the security forces and civilians.

According to an official from the US-led coalition who spoke on condition of anonymity, IS is now "stretched" financially and its operations in Iraq are "very localised".