Iraq's prime minister, Nouri al-Maliki, has repeatedly accused Saudi Arabia and Qatar of openly funding ISIS, though there is no evidence that this is the case.
The group is also believed to be receiving considerable funds from their operations in Eastern Syria, where the group has commandeered oil fields and engages in the out-smuggling of raw materials and archaeological artifacts.
ISIS also generates revenue from producing crude oil and selling electric power in northern Syria. The crude oil is reportedly sold back to the Syrian government.
In mid-2014, Iraqi intelligence extracted information from an ISIS operative that revealed the organization had more than $2bn.
According to the Associated Press ISIS has also taken effective control of Tikrit, where Saddam Hussein was born.
