Iraqi officials following the ISIS money trail now estimate that the insurgent army seeking to establish a Sunni caliphate in the Middle East now has approximately $2 billion at its disposal. Even with all the electronics and monitoring available to global intelligence units, the source of the bulk these funds remains unknown, at least officially.

Nouri al-Maliki, the prime minister of Iraq, holds Saudi Arabia responsible for massive funding of the Sunni jihadist army (officially named the Islamic State of Iraq and the Levant). The Kingdom of Saudi Arabia – the world’s major oil exporter – is a major ally to the United States and has denied al-Maliki’s accusation. A spokesperson for the U.S. State Department, Jen Psaki, has charaterized the Premier’s statement as “inaccurate and humiliating.”

In a carefully worded statement, Charles Lister said that “no publicly accessible proof exists” that any state has been involved in either the financing or creation of ISIS. Lister is a Visiting Fellow Qatar’s Brookings Doha Center, a part of the Brookings Institution, a generally centrist think tank based in Washington, D.C.

With tools are their disposal like high-technology weaponry and well maintained vehicles, ISIS’ 10,000 rebel fighters are highly resourced to commit plunder. The mountains of money to support it all is certainly coming from somewhere. 

Al-Maliki said that a regional conspiracy exists, one backed by “massive media” support. Indeed, media funded by Saudi Arabia and Qatar have described the militants as revolutionaries. On the other hand, officials from the U.S. have put the blame on al-Maliki himself, pointing to a split caused by his warned-about sectarian domestic policies.

No publicly-accessible proof exists that Saudi Arabia – or any other Gulf state – is part of the ISIS money trail. Saudi Prince Miteb Bin Abdullah has said that his kingdom is categorically opposed to sectarianism and violence – historically and currently – and refuses “to intervene in the interior affairs of another state.”

Gunter Meyer, however, takes clear exception to this. He is the director of Germany’s Center for Research on the Arabic World at Johannes Gutenberg University of Mainz and has said that ISIS’ greatest support has come from Gulf states, primarily Saudi Arabia. He named other financial supporters, specifically Kuwait, Qatar and the United Arab Emirates. The motivation in funding the Sunni rebel army, he said, has been to oppose Syria’s President Bashar al Assad. Although Syria’s ruling elite are mostly from Alawite, a Shiite offshoot, the clear majority of Syria’s population is are Sunni Muslims.

Otherwise, the flow of money from private donors is suspected and untold funds are flowing from now-Islamist-controlled oil fields of northern Syria. Lister of Brookings believes that ISIS largely funds itself at this point, generating funds from extortion, kidnapping, smuggling and, lately, bank robbery: the terrorist group stole $430 million last week from a bank in Mosul.

According to Lister, a big part of the ISIS money trail is extortion, which is widespread, affecting “small businesses and big companies, construction firms, and if the rumors are true, even local government representatives.” He adds that taxes are now being levied in the areas controlled by ISIS, “for example Raqqa in northeastern Syria.”