IS threat 'beyond anything we've seen' - Pentagon

Washington - The sophistication, wealth and military might of Islamic State militants pose a major threat to the United States that may surpass that from al-Qaeda, US military leaders said on Thursday.

"They are an imminent threat to every interest we have, whether it's in Iraq or anywhere else," Defence Secretary Chuck Hagel told reporters at the Pentagon about the militant group, which has seized a third of Iraq and released a video this week showing one of its fighters beheading an American hostage.

Asked if Islamic State posed a threat to the United States comparable to that of the attacks of  11 September 2001, Hagel said the group was "as sophisticated and well-funded as any group we have seen.

"They are beyond just a terrorist group. They marry ideology, a sophistication of ... military prowess. They are tremendously well-funded. This is beyond anything we've seen."

General Martin Dempsey, chairperson of the US Joint Chiefs of Staff, said the group could pose a direct threat to Western countries through the return of European or US nationals to their home countries after having fought in Syria or Iraq.