WASHINGTON (AP) — Islamic State militants once relied on wealthy Persian Gulf donors for money.

But the extremist group now has a self-sustaining financial juggernaut, earning more than $3 million a day from oil smuggling, human trafficking, theft and extortion.

That's according to U.S. intelligence officials and private experts.

American intelligence officials say the group's resources exceed that of any other terrorist organization in history.

And analysts say the Islamic State group, which has taken over large parts of Syria and Iraq, controls as many as 11 oil fields in both countries.

(Story by: Ken Dilanian, Intelligence Writer, The Associated Press)