Turkish Interior Ministry has identified the bomber in Sunday’s Ankara attack as 24-year-old Seher Cagla Demir.
The ministry said in a statement Tuesday that Demir joined the PKK terrorist group in 2013 and received training with the YPG in Syria.
YPG is the militant wing of the Syrian terrorist group PYD.
Demir was registered in Turkey's eastern province of Kars's Kagizman district.
"May Allah rest the souls of the victims and we offer condolences to their families and the nation. We wish the wounded people a quick recovery as well," the statement said.
The car bomb attack in Ankara’s central Kizilay neighborhood Sunday evening hit a major public transportation hub, killing 37 people and injuring dozens others.
Later Tuesday, the U.S. administration did not verify the information, saying it has not seen the reports that the attacker has crossed the border into Syria and was trained.
Reiterating that PKK was a terrorist organization and that Turkey had every right to defend itself, the U.S. State Department said it recognized the threat that the group continued to pose to the people of Turkey.
The U.S. considers PYD, which is the Syrian affiliate of PKK, as an effective group in Syria fighting Daesh.
Turkey, on the other hand, considers PYD as a terrorist group.
Since the attack, some media has reported a message was supposedly published by the U.S. embassy in Ankara two days before the attack that warned Americans to stay away from city’s center.
Some reports even said the U.S. might have gotten intelligence from the terrorist PKK group.
The State Department's John Kirby said the American embassy in Ankara received information from Turkish authorities and then issued a statement to warn its citizens. He also rejected reports that the U.S. in any way cooperated or assisted the PKK, calling the claims "absolutely ridiculous".
Though Turkey and the U.S. do not agree on everything, Kirby said the recent intelligence sharing showed that the relationship between both countries remained strong in the face of these kind of threats.