Baghdad, Dec 13 (IANS): Iraqi finance minister Hoshyar Zebari has said that the Islamic State (IS) is smuggling Iraqi and Syrian oil via Turkey, and called it the richest terrorist group in the world.

"IS controls a number of oilfields in Syria and Iraq and they smuggle this oil overland through trucks, through middlemen to Turkey or towards other countries," Zebari told Al-Jazeera news channel Friday.

After an accounting of banks under IS control, Zebari said that the IS is now believed to have looted about $500 million from Mosul, Tikrit and other cities, saying it was "the richest armed group in the world".

He said Iraq was trying to crack down on IS financing, including oil smuggling.

"The air campaign targets these facilities in Syria and in northern Iraq in order to deprive them of this revenue but they have enormous financial resources; they are paying recruits good salaries, better than what we can afford to pay ours," he added.

"And this is one element of the strength of this organisation. It's not purely an underground terrorist organisation. It has an agenda it wants to control. It wants to rule."

He also rejected comments by US officials that the fight against the IS could take years.

"Contrary to what many people think, I don't think this will be a long drawn out battle," the minister said.

The comments came after the Iraqi army managed to liberate two key districts in the city of Samarra Friday.

He added that coordination between Iraqi forces and the US-led coalition is the key to the success of the offensive against the radical group.