Top US official says IS is world's wealthiest terrorist group

A top United States administration official has termed the Islamic State (IS) world's wealthiest terror group that generates tens of millions of dollars a month from "deep and diverse" sources that include, black market oil sales, ransoms and extortion.

David Cohen, Treasury under-secretary for terrorism and financial intelligence, said on Thursday that the terror group is the "best-funded terrorist organization" confronted by the U.S., reported News 24.

Cohen said that the group earns about 1 million dollars a day alone by selling crude oil from the oil fields captured in Iraq and Syria. He added that since the group has amassed wealth at "an unprecedented pace" than other terror groups, it presents a difficult challenge to the U.S. and its allies attempting to choke off money flows to the outfit.

The official, who is leading the fight against the IS, also noted that unlike Al Qaeda, the IS does not attract most of its funds from rich donors in Gulf countries or from state sponsors.

Cohen added that there is no secret weapon to "empty IS' coffers overnight" and that the fight to take on the group will be a "sustained fight.