Since taking Mosul earlier this month, the Islamic militant group ISIS has robbed banks, committed mass executions, and burned oil refineries as Iraq slides closer and closer to all-out war. According to NYPD counterterrorism chief John Miller, New Yorkers and other Americans are marching in their ranks.

Miller estimates there are more than 100 Americans currently fighting alongside groups like ISIS in Iraq and Syria, though he has not said exactly how many or how he came about the information. The terror chief expressed worry that American jihadists would attempt violence upon their return to the country. From the New York Daily News:

"I would be hyper-concerned about the people over there from New York City on the presumption they're going to return to New York City," John Miller, said Thursday.

Miller said he is just as worried about American jihadists from "Chicago, Minnesota, Portland, you name it."

"If their mindset is to return to America and to engage in terrorist activities, they're likely going to end up in New York anyway," Miller said.

This morning, what appears to be an ISIS recruitment video titled "There Is No Life Without Jihad" surfaced online, featuring a group of British and Australian jihadists urging Westerners to join the movement.

[Image via AP]