Erdogan says 'no doubt' Syrian Kurdish fighters behind Ankara attack

Firefighters try to extinguish flames following an explosion after an attack targeted a convoy of military service vehicles in Ankara on February 17, 2016

President Recep Tayyip Erdogan said on Friday that Turkey had "no doubt" that Syrian Kurdish fighters were behind the attack on a convoy of military buses in Ankara that left 28 dead.

"We have no doubt that the perpetrators are the YPG and PYD," Erdogan said in Istanbul, referring to the main Syrian Kurdish militia and their political wing.

Ankara has insisted that the Syrian Kurdish People's Protection Units (YPG) and Democratic Union Party (PYD) were behind the attack, although its confidence has met with scepticism from chief NATO ally the United States.

The suicide car bomb attack Wednesday -- blamed on a Syrian suicide car bomber -- struck at the heart of Ankara an an area where institutions including the army headquarters and parliament are concentrated.

"Who was the suicide bomber? Of course he was from the YPG," said Erdogan.

The attack risks further straining ties between Turkey and the United States, which works with the YPG as an effective force in the fight against Islamic State (IS) jihadists in Syria.

Erdogan said Turkey was "saddened" by the stubbornness of the West in not linking the YPG to the Kurdistan Workers' Party (PKK) which has waged a three-decade insurgency against the Turkish state and is recognised as a terror group by the United States and EU.

He added he would speak to US President Barack Obama by phone later Friday to warn him over "the weapons support they (the United States) give to those organisations," referring to the PYD and YPG.

"This incident will help our friends -- who have so far failed to be convinced -- better understand how strong the links are between the YPG and PYD in Syria and the PKK in Turkey," he said.

But US State Department spokesman John Kirby said Thursday that it was still an "open question" who had carried out the Ankara attack.

"We're in no position to confirm or deny the assertions made by the Turkish government with respect to responsibility," said Kirby.

But Erdogan refused to be drawn into a debate with Kirby, who has angered Turkey by repeatedly defending US support of the YPG in the last days.

"He (Kirby) is not my interlocutor. I am going to speak to Obama at five (1500 GMT)," Erdogan said.