An Islamic State militant uses a loud-hailer to announce to residents of Taqba city that Tabqa air base has fallen to Islamic State militants, in nearby Raqqa city August 24, 2014. CREDIT: REUTERS/STRINGER
IN PHOTO: An Islamic State militant uses a loud-hailer to announce to residents of Taqba city that Tabqa air base has fallen to Islamic State militants, in nearby Raqqa city August 24, 2014. REUTERS/STRINGER

While the radical ISIS in Syria got bombed by a massive airstrike launched by the United States and its Arab allies, a number of its American members have crept back home in the mainland U.S.

The National Counterterrorism Centre earlier estimated more than 100 Americans left the country to join either the ISIS or the al-Nusra Front, which claims ties to Al Qaeda. Now, it is believed 40 of those have returned back home, probably just lurking in the background, awaiting instructions when to strike.

The centre said the information has been forwarded to the FBI, who are looking at all those "who've gone, those who've tried to go, some who've come back and are under active."

The National Counterterrorism Centre's announcement merely was an admission and confirmation to Rep. Tim Bishop's remarks on Sept 12 that a number of American ISIS jihadi fighters are already back in the U.S. after training in Syria.

John Miller, NYPD's terror chief, believes New York City could be the group's ultimate target. He said they are currently looking into a number of people, in coordination with the FBI's Joint Terrorism Task Force. But so far they have yet to establish that their suspects have actual ties to the ISIS.

"There is a small number of people we're looking at in the New York area," Miller said. "Beyond that, if evidence is developed that a person worked for, or fought for a designated terrorist organization, they will be prosecuted."

In June, King ­Abdullah of Saudi Arabia warned authorities in Europe and the United States to be extra vigilant as members of the ISIS terror group could already be in their respective countries, preparing to unleash terrifying atrocities.

Dr Peter Pry, a former CIA officer, had earlier remarked that the ISIS could initially target the U.S.' power grid as it carries out its terror strike against the superpower.

­Abdullah said the Western children do not stand a chance. "You see how they [jihadists] carry out beheadings and make children show the severed heads in the street."

Apart from beheadings, experts anticipate massive human casualties from biological weapons.