A Turkey-based Kurdish militant group has said it carried out Wednesday's bomb attack in Ankara that killed 28 people.
The Kurdistan Freedom Hawks (TAK) group said on its website that the attack was retaliation against the policies of President Recep Tayyip Erdogan.
Earlier, Mr Erdogan said he had "no doubt" that US-backed Syrian Kurdish groups carried out the bombing.
The TAK was once linked with the outlawed Kurdistan Workers Party (PKK).
Both the TAK and the PKK are classified as terrorist groups by Turkey and the US.
In a statement, the TAK said a 27-year-old Turkish national, Abdulbaki Sonmez, had carried out Wednesday's rush-hour car-bombing on a Turkish military convoy in the country's capital.
The group made reference to military operations against Kurdish rebels in south-east Turkey, and threatened more attacks.
Turkey had blamed a Syrian national and member of the People's Protection Units (YPG) for the bomb attack.
The Turkish government insists that the YPG and the Syrian Kurdish Democratic Union Party (PYD) played a role in Wednesday's attack.
But the US, a key ally of Turkey, has cast doubt on this.
The US supports the PYD and its military wing, the YPG, in the fight against so-called Islamic State (IS) in Syria.
Both groups are adamant they are not branches of the PKK and have dismissed suggestions they had any involvement in the attack.
State Department spokesman Mark Toner denied Turkish assertions that the US had supplied weapons direct to the YPG.
Mr Toner also said he could not substantiate claims that the YPG was smuggling US weapons to the PKK.
The US does however concede that it has air-dropped weapons to a Kurdish-Arab coalition - of which the YPG is a part - who are fighting Islamic State.
The coalition recently announced they had taken the town of Shahadi in the Syrian province of al-Hassakah, cutting strategic links between IS forces in Syria and Iraq.
Continued American support for Syrian Kurds, reiterated by a state department spokesman this week, is threatening to cause a rift between the two countries.
As the Syrian army, backed by Russian air power, has targeted Syrian opposition forces and pushed further north in Aleppo province, the Syrian Kurdish militia has made gains from the rebels close to the Turkish border.
Turkey fears they could seize a 100km-stretch (62 miles) as far as Jarablus to create a large zone along the border.
The army has continued to shell YPG targets across the border near the rebel-held town of Azaz.