ISIS stole more than $800 million from Iraqi banks when it captured the predominantly Sunni provinces in the northern and western parts of the country in 2014, the Central Bank of Iraq reported Wednesday.

"Most of the deposits belong to the local government departments and were related to provincial projects outlined in the 2014 budget, including assets from the Ministries of Defense and Interior," the statement read.

The terrorist group seized 121 branches from private and state-owned banks, including the CBI branch in Mosul, and became one of the richest extremist groups in history, with its income amounting to $2 billion annually.

ISIS, though, has continued to lose territory with primary revenue-generating streams drying up. So far, ISIS has lost 27,000 square miles — 78 percent of its holdings in Iraq and 58 percent in Syria — since the group's peak control in early 2015, said Brett McGurk, senior envoy to the U.S.-backed coalition.

ISIS's revenue dropped from $1.9 billion in 2014 to about $870 million in 2016, according to a report in Newsweek, and in 2017 lost 80 percent of its once-exorbitant income.

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