ROBERT SIEGEL, HOST:
Turkish officials say Islamic State militants orchestrated the terrorist attack that killed 42 people and injured more than 230 at Istanbul's Ataturk Airport yesterday. ISIS has not claimed responsibility. CIA Director John Brennan told an audience in Washington that the group may never do so.
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JOHN BRENNAN: Well, to my knowledge there is no credible claim of responsibility at this point. But that's not very surprising because at least in most instances, if not all, ISIS has not claimed credit or responsibility for attacks that are perpetrated inside of Turkey.
SIEGEL: NPR's counterterrorism correspondent Dina Temple-Raston is following the investigation, and she joins us now. And, Dina, before we get to the details of the investigation, I want you to explain what the CIA director just said. Why doesn't ISIS claim responsibility for attacks inside Turkey?
DINA TEMPLE-RASTON, BYLINE: Well, CIA Director Brennan was talking to the Council on Foreign Relations in Washington, and he said that ISIS carries out these attacks to send a signal to Turkish officials to put them on notice, if you will. But the group doesn't claim responsibility outright because it doesn't want to alienate Turks who might be sympathetic to their cause.
There was a suicide bombing on a shopping district in Istanbul at the end of March. And four people were killed, and 36 were wounded. And ISIS never took formal responsibility. In the past six months, there have been four deadly attacks in Turkey, and most of them were connected to a Kurdish separatist group called the PKK.
In this case, the Turkish government has been very, very quick to say that they suspect this is ISIS, and Brennan seemed to confirm their suspicions.
SIEGEL: Well, what have they - what have Turkish investigators discovered so far that leads them to believe that it's ISIS?
TEMPLE-RASTON: Well, right now the evidence is circumstantial. The PKK as a general matter has limited itself to military and police targets inside Turkey. Civilian targets like this fit much more into ISIS's attack profile. The way the attack unfolded in Istanbul is very reminiscent of both the November 13 attacks in Paris and the airport attack in Brussels this past May.
ISIS took responsibility for both those attacks.
In the November 13 attacks, there were a number of gunmen who, as you remember, fanned out across Paris and just opened fire on people in cafes and at a concert hall. And then the gunmen ignited these explosive vests. That appears to be exactly what happened in Istanbul. And then during the Brussels Airport attack, gunmen stored the - stormed the departure hall just like they did last night in Istanbul. So that's why U.S. officials are saying this attack has as - in their words - all the hallmarks of ISIS.
SIEGEL: Apart from those hallmarks of ISIS, what are your sources telling you about this investigation?
TEMPLE-RASTON: We spoke to U.S. officials who'd been briefed and what we understand they know so far is that there are at least three foreign nationals who were involved. Investigators in Turkey interviewed and released the taxi driver who had actually dropped the attackers off at the airport at 10 p.m. local time last night. And we understand that he was very helpful to the investigation.
And, again, if you look at the Brussels attacks back in May, the taxi driver who dropped off the attackers was a goldmine of information for police. He took them back to the building where he picked up the attackers, and inside the police found the apartment where the bombs were constructed. They found fingerprints that belonged to accomplices, so that was really a key to that investigation. And Turkish officials are hoping for something similar this time around.
SIEGEL: That's NPR's counterterrorism correspondent Dina Temple-Raston. Dina, thanks.
TEMPLE-RASTON: You're welcome. Transcript provided by NPR, Copyright NPR.