ISIS threatens Washington; US agencies working 'feverishly' to uncover plot, says CIA chief

Cairo: Islamic State warned in a new video on Monday that countries taking part in air strikes against Syria would suffer the same fate as France, and threatened to attack in Washington.

The video, which appeared on a site used by Islamic State to post its messages, begins with news footage of the aftermath of Friday's Paris shootings in which at least 129 people were killed.

The message to countries involved in what it called the "crusader campaign" was delivered by a man dressed in fatigues and a turban, and identified in subtitles as Al Ghareeb the Algerian.

"We say to the states that take part in the crusader campaign that, by God, you will have a day, God willing, like France's and by God, as we struck France in the center of its abode in Paris, then we swear that we will strike America at its center in Washington," the man said.

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It was not immediately possible to verify the authenticity of the video, which purports to be the work of Islamic State fighters in the Iraqi province of Salahuddine, north of Baghdad.

Soon after the video surfaced, CIA director John Brennan warned on Monday that the attacks in Paris were likely not a "one off event" and that he expects Islamic State has more operations in the pipeline.

"Security and intelligence services right now are working feverishly to see what else they can do in terms of uncovering it," he said at a Washington think tank.

The CIA chief said Friday night's attacks by gunmen in suicide vests in the heart of the French capital were carefully planned and executed.

"This was not something done in a matter of days. This is something that was carefully and deliberately planned over the course of several months in terms of whether they had the operatives, the weapons, explosives, suicide belts.

"I would anticipate that this is not the only operation ISIL has in the pipeline," he said, using an alternate acronym for IS, the militant group that has seized large areas of Syria and Iraq.

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Meanwhile, the French government has called the Paris attacks an act of war and said it would not end its air strikes against Islamic State in Syria and Iraq. French fighter jets launched their biggest raids in Syria to date on Sunday targeting the Islamic State's stronghold in the city of Raqqa. The operation was carried out in coordination with U.S. forces.

Police raided homes of suspected Islamist militants across France overnight following the Paris attacks. "Al Ghareeb the Algerian" also warned Europe in the video that more attacks were coming.

"I say to the European countries that we are coming, coming with booby traps and explosives, coming with explosive belts and (gun) silencers and you will be unable to stop us because today we are much stronger than before," he said.

Apparently referring to international talks to end the Syrian war, another man identified in the video as Al Karrar the Iraqi tells French President Francois Hollande "we have decided to negotiate with you in the trenches and not in the hotels."