U.S. defense chief expresses condolences over Istanbul attack

U.S. Secretary of Defense Ash Carter had called his Turkish counterpart to express condolences in the wake of an attack at the Ataturk Airport in Istanbul that killed at least 41 people, the Pentagon said on Wednesday.

"Secretary Carter strongly condemned the terrorist attack in Istanbul as a cowardly assault on a stalwart NATO ally and enduring partner in our efforts to confront the threat of terrorism," said the Pentagon in a statement.

U.S. military will "work closely and resolutely" with Turkish allies to defeat terrorists, it added.

At least 41 people were killed and more than 200 others injured in explosions that hit Ataturk Airport on Tuesday.

Turkish media reported that Turkey's intelligence units sent a warning letter to related state institutions about potential attacks by the Islamic State (IS) militants nearly 20 days ago.

Hande Firat, CNNTurk's representative in Ankara, said on a live broadcast that the Ataturk Airport was listed as a potential target in the letter.

As of now, no group has claimed responsibility for the attacks.

However, U.S. House Homeland Security Committee Chairman Michael McCaul said on Wednesday that IS was most likely behind Tuesday's attack.

"I believe this most likely is an ISIS attack yesterday in Istanbul," said McCaul in an interview with MSNBC, referring to another acronym of the extremist group.

"This was like a sequel to Brussels but far more deadly than Brussels was," said McCaul.

Turkish Prime Minister Binali Yildirim also blamed the IS for the atrocity, though he said efforts were continuing to identify the perpetrators. Endit