Islamic State is reported to have $2bn (£1.2bn) in cash and assets, making it the world's wealthiest militant group. Initially, much of its financial support came from individuals in Arab Gulf states. Today, IS is a largely self-financed organisation, earning millions of dollars a month from the oil and gas fields it controls, as well as from taxation, tolls, smuggling, extortion and kidnapping. The offensive in Iraq has also been lucrative, giving it access to cash held in major banks in cities and towns it has seized.