Turkey's prime minister has dismissed a Turkey-based Kurdish militant group's claim of responsibility for an attack in Ankara that killed 28 people, insisting it was carried out by a U.S.-backed Syrian Kurdish militia group.

The Kurdistan Freedom Falcons, TAK, claimed the suicide car bomb attack on Friday, saying it was in retaliation for Turkish military operations against militants in southeast Turkey. The group is an offshoot of the outlawed Kurdistan Workers Party, or PKK.

But Ahmet Davutoglu told reporters Saturday that Turkey was certain that the Syrian Kurdish group was behind the bombing. He said TAK took responsibility to ensure the militia's "international legitimacy" was not harmed.

Davutoglu again called on the United States not to back the group and to show solidarity with Turkey "without ifs or buts."